Categories: Synthesis of N-Heterocycles > benzo-fused N-Heterocycles >
Synthesis of quinolines
Name Reactions
Recent Literature
Heteroaromatic tosylates and phosphates are suitable electrophiles in
iron-catalyzed cross-coupling reactions with alkyl Grignard reagents. These
reactions are performed at low temperature allowing good functional group
tolerance with full conversion within minutes.
T. M. Gøgsig, A. T. Lindhardt, T. Skrydstrup, Org. Lett., 2009,
11, 4886-4888.
The success of a one-step transformation of heterocyclic N-oxides to
2-alkyl-, aryl-, and alkenyl-substituted N-heterocycles hinges on the
combination of copper catalysis and activation by lithium fluoride or magnesium
chloride. The utility for the scaffold decoration of a broad range of complex
N-heterocycles is exemplified by syntheses of new structural analogues of
several antimalarial, antimicrobial, and fungicidal agents.
O. V. Larionov, D. Stephens, A. Mfuh, G. Chavez, Org. Lett., 2014,
16, 864-867.
A heterogeneous cobalt oxide is an effective catalyst for aerobic
dehydrogenation of various 1,2,3,4-tetrahydroquinolines to the corresponding
quinolines in good yields under mild conditions. Other N-heterocycles are
also successfully oxidized to their aromatic counterparts.
A. V. Iosub, S. S. Stahl, Org. Lett.,
2015,
17, 4404-4407.
A reusable phenalenyl-based photocatalyst mediates an oxidative
dehydrogenation of saturated N-heterocycles and alcohols in the presence
of molecular oxygen as a greener oxidant. A wide variety of N-heteroaromatics,
such as quinoline, carbazole, quinoxaline, acridine, and indole derivatives, as
well as aldehydes and ketones, were successfully synthesized.
V. Pathania, S. R. Roy, J. Org. Chem., 2024, 89,
4145-4155.
A visible-light-mediated aerobic dehydrogenation reaction enables a simple and
environmentally friendly method for synthesizing N-containing
heterocycles using a nontoxic, stable, and inexpensive titanium dioxide catalyst
and oxygen as green oxidant. The reaction provides a variety of substituted
quinolines, indoles, quinoxalines, and 3,4-dihydroisoquinolines.
J. Noh, J.-Y. Cho, M. Park, B. Y. Park, J. Org. Chem., 2023, 88,
10682-10692.
o-Quinone-based catalysts enable an oxidative dehydrogenation of
tetrahydroquinolines to afford quinolines. Use of a Co(salophen) cocatalyst
allows the reaction to proceed efficiently with ambient air at room temperature.
The utility of the catalytic method is demonstrated in the preparation of a
number of medicinally relevant quinolines.
A. E. Wendlandt, S. S. Stahl, J. Am. Chem. Soc., 2014,
136, 11910-11913.
Visible light-mediated metallaphotoredox catalysis enables a highly
chemoselective deoxygenation of N-heterocyclic N-oxides using
Hantzsch esters as the stoichiometric reductants and only a tiny amount of the
catalyst within a few minutes at room temperature. The reaction tolerates a wide
range of functional groups, such as carbamates, esters, ketones, nitrile groups,
nitro groups, and halogens.
J. H. An, K. D. Kim, J. H. Lee, J. Org. Chem., 2021, 86,
2876-2894.
Visible-light mediates a scalable and operationally simple method for the
chemoselective deoxygenation of a wide range of N-heterocyclic N-oxides
at room temperature using only commercially available reagents. This protocol
offers an unprecedented chemoselective removal of the oxygen atom in a quinoline
N-oxide in the presence of a pyridine N-oxide through the
judicious selection of the photocatalyst.
K. D. Kim, J. H. Lee, Org. Lett.,
2018, 20, 7712-7716.
A single-step conversion of various N-vinyl and N-aryl amides
to the corresponding pyridine and quinoline derivatives involves amide activation with trifluoromethanesulfonic anhydride in the
presence of 2-chloropyridine followed by π-nucleophile addition to the activated
intermediate and annulation. Compatibility of this chemistry with various functional groups is
noteworthy.
M. Movassaghi, M. D. Hill, O. K. Ahmad, J. Am. Chem. Soc.,
2007,
129, 10096-10097.
The direct conversion of amides, including sensitive N-vinyl amides,
to the corresponding trimethylsilyl alkynyl imines followed by a
ruthenium-catalyzed protodesilylation and cycloisomerization gives various
substituted pyridines and quinolines.
M. Movassaghi, M. D. Hill, J. Am. Chem. Soc.,
2006, 128, 4592-4593.
ZnMe2 promotes a direct C2- or C4-selective primary and secondary
alkylation of a broad range of pyridines and quinolines using 1,1-diborylalkanes
as alkylation sources. While substituted pyridines and quinolines exclusively
afford C2-alkylated products in good yields, simple pyridine delivers
C4-alkylated pyridine with excellent regioselectivity.
W. Jo, S.-y. Baek, C. Hwang, J. Heo, M.-H. Baik, S. H. Cho, J. Am. Chem. Soc.,
2020, 142, 13235-13245.
Pd(OAc)2/2,4,6-Collidine/Brønsted acid catalyze an aerobic oxidative
aromatization of simple aliphatic alcohols and anilines to provide diverse
substituted quinoline derivatives in high yields with wide functional group
tolerance. Practically, the protocol can be easily scaled up to gram-scale.
J. Li, J. Zhang, H. Yang, G. Jiang, J. Org. Chem.,
2017, 82, 3245-3251.
A Pd-catalyzed decarbonylative Suzuki cross-coupling of widely available
heterocyclic carboxylic acids with arylboronic acids enabled the straightforward
preparation of >45 heterobiaryl products using pyridines, pyrimidines,
pyrazines, and quinolines in very good yields.
A. Cervantes-Reyes, A. C. Smith, G. M. Chinigo, D. C. Blakemore, M. Szostak, Org. Lett.,
2022, 24, 1662-1667.
An acidic I2-DMSO system converts readily available aspartates/phenylalanines
and anilines into alkyl quinoline-3-carboxylates/3-arylquinolines. While DMSO is
activated by HI via a Pummerer reaction, I2 mediates a Strecker
degradation of the the amino acid. A formal [3 + 2 + 1] annulation of these two
concurrently generated C1 and C2 synthons with aniline provides the quinoline
core.
J.-T. Ma, T. Chen, B.-C. Tang, X.-L. Chen, Z.-C. Yu, Y. Zhou, S.-Y. Zhuang,
Y.-D. Wu, J.-C. Xiang, , J. Org. Chem., 2023, 88,
3714-3723.
A [3+1+1+1] annulation of arylamines, arylaldehydes and dimethyl sulfoxide
(DMSO) provides 3-arylquinolines in very good yields. In this
annulation, arylamines provide two carbon atoms and one nitrogen atom,
arylaldehydes furnish one carbon atom, and DMSO provides two nonadjacent
methines (=CH-).
T. Yang, H. Li, Z. Nie, M.-d. Su, W.-p. Luo, Q. Liu, C.-C. Guo, J. Org. Chem., 2022, 87,
2797-2808.
A phenalenyl-based molecule catalyzes a transition-metal-free C-alkylation
via a borrowing hydrogen pathway for α-alkylations of ketones, synthesis of substituted quinolines, and 9-monoalkylations of fluorene. A preliminary
investigation of the reaction mechanism has been carried out, suggesting a
radical-mediated borrowing hydrogen pathway.
A. Banik, P. Datta, S. K. Mandal, Org. Lett., 2023, 25,
1305-1309.
Readily available Co(OAc)2·4 H2O catalyzes convenient and efficient dehydrogenative cyclizations of 2-aminoaryl alcohols and ketones
or nitriles to provide quinolines or
quinazolines in good yields in one pot under mild conditions. The present
protocols offer an environmentally benign approach for the synthesis of
N-heterocycles in good yields.
Z. Hao, X. Zhou, Z. Ma, C. Zhang, Z. Han, J. Lin, G.-L. Lu, J. Org. Chem., 2022, 87,
12596-12607.
A simple metal-ligand cooperative approach enables dehydrogenative
functionalization of benzylic alcohols to various substituted quinolines and
quinazolin-4(3H)-ones in good yields under relatively mild reaction
conditions using simple and easy-to-prepare air-stable Cu(II) complexes
featuring redox-active azo-aromatic scaffolds.
S. Das, S. Sinha, D. Samanta, R. Mondal, G. Chakraborty, P. Brandaõ, N. D.
Paul, J. Org. Chem., 2019,
84, 10160-10171.
An efficient copper-catalyzed intermolecular decarboxylative cascade cyclization
of aryl aldehydes, anilines, and acrylic acid permits the direct synthesis of
2-substituted quinolines. This method features promising chemo- and
regioselectivity and also tolerates a wide variety of substrates with excellent
functional-group tolerance, high yields, a radical reaction pathway, and aerobic
reaction conditions.
R. Chatterjee, M. Pothireddy, R. Dandela, Synlett, 2023,
34,
1058-1062.
A simple, phosphine-free, and inexpensive catalytic system based on a
manganese(II) complex mediates the synthesis of different important N-heterocycles
such as quinolines, pyrroles, and pyridines from amino alcohols and ketones.
A. Maji, S. Gupta, M. Maji, S. Kundu, J. Org. Chem., 2022, 87,
8351-8367.
A convenient and eco-friendly nickel-catalyzed synthesis of quinoline and
quinoxaline via double dehydrogenative coupling starting from 2-aminobenzyl
alcohol/1-phenylethanol and diamine/diol, respectively, operates at mild
reaction temperatures. The inexpensive molecularly defined catalyst can easly be
regenerated under aerobic/O2 oxidation.
A. K. Bains, V. Singh, D. Adhikari, J. Org. Chem., 2020, 85, 14971-14979.
An annulation between 2-aminobenzyl alcohols, benzaldehydes, and DMSO
provides quinolines. Interestingly, introducing substituent groups to the
α-position of sulfoxides resulted in the interchange of the positions between
benzaldehydes and sulfoxides in the product quinolines.
T. Yang, Z.-w. Nie, M.-d. Su, H. Li, W.-p. Luo, Q. Liu, C.-C. Guo, J. Org. Chem., 2021, 86,
15232-15241.
A visible-light-mediated oxidative cyclization of 2-aminobenzyl alcohols with
secondary alcohols provides quinolines in good yields at room temperature. This
photocatalytic method employes anthraquinone as an organic small-molecule
catalyst and DMSO as an oxidant.
J.-x. Xu, N.-l. Pan, J.-x. Chen, J.-w. Zhao, J. Org. Chem., 2021, 86,
10747-10754.
A palladium catalyzed annulation of o-iodo-anilines with propargyl
alcohols provides a broad range of 2,4-disubstituted quinolines under mild
conditions. The reaction tolerates diverse functional groups.
Z. Zhang, J.-T. Deng, J.-Y. Feng, J.-Y. Liang, X.-T. Xu, J.-B. Peng, J. Org. Chem., 2023, 88,
12054-12063.
Treatment of 2-arylethylmagnesium bromides, prepared from 2-arylethyl bromides
and magnesium, with aromatic nitriles, followed by reaction with water and then
with N-iodosuccinimide under irradiation with a tungsten lamp, provides
2-arylquinolines in good yields under transition-metal-free conditions.
2-Alkylquinolines could be also obtained in moderate yields.
H. Naruto, H. Togo, Synthesis, 2020, 52,
1122-1130.
A simple and efficient reaction of 2-vinylanilines and benzyl halides provides
various 2-arylquinolines in good yields. This
reaction is additive free and is catalyzed by the in situ released HBr. The present
synthetic route offers high functional group tolerance and a simple work-up.
Q. Han, S. Li, Z. Cai, C. Ding, L. Feng, C. Ma, Synthesis, 2022, 54,
4818-4826.
FeCl3-catalyzed decyanation of α-aminonitriles followed by [4 + 2]
annulation with terminal alkynes provide a broad range of 2,4-diaryl quinolines
in good yields via a Povarov-type [4 + 2] annulation from in situ generated
iminium species. The synthetic application of this strategy includes gram-scale
synthesis and a continuous-flow process for shorter reaction time.
S. Sathyendran, K. Muthu, K. Govindan, N.-Q. Chen, W.-Y. Lin, G. C. Senadi, Org. Lett., 2023, 25,
4086-4091.
A visible-light-driven aza-6π electrocyclization of 2-styrylanilines with
aromatic aldehydes provides 2,3-disubstituted quinolines smoothly at room
temperature. This protocol relies on the EDA complexes of AlCl3 with
imine to induce an absorption red-shift to match the visible light of
blue-light-emitting diodes.
Q.-L. Zhang, B. Sun, G. Ji, G. Zhang, F.-L. Zhang, Org. Lett., 2024,
26,
110-115.
Visible-light-excited 9,10-phenanthrenequinone (PQ*) catalyzes a mild and
efficient electrocyclization of 2-vinylarylimines for the synthesis of 2,4-disubstituted
quinolines in very good yields.
J. Talvitie, I. Alanko, E. Bulatov, J. Koivula, T. Pöllänen, J. Helaja, Org. Lett., 2022, 24,
274-278.
The use of hydrazine under basic conditions enables an efficient and general
construction of quinoline N-oxides from ortho-nitro chalcones via
umpolung of carbonyl groups. This transition-metal free method offers good functional group tolerance, environmental
friendliness, and mild reaction conditions with nitrogen gas as byproduct.
G. Zhang, K. Yang, S. Wang, Q. Feng, Q. Song, Org. Lett., 2021, 23,
595-600.
The use of hypervalent iodine(III) carboxylates as alkylating agents enables a
highly site-selective alkylation of heteroarene N-oxides in the presence of
a cheap copper catalyst under visible light conditions. This mild method
proceeds at room temperature in an air atmosphere.
D.-Y. Liu, X. Liu, Y. Gao, C.-Q. Wang, J.-S. Tian, T.-P. Loh, Org. Lett., 2020, 22, 8978-8983.
Eosin Y catalyzes a visible-light-promoted C2 selective arylation of quinoline and
pyridine N-oxides with diaryliodonium tetrafluoroborate as an arylation reagent under mild conditions. This methodology
offers high regioselectivity, simple operation and good functional group tolerance.
D. Li, C. Liang, Z. Jiang, J. Zhang, W.-T. Zhuo, F.-Y. Zou, W.-P. Wang, G.-L.
Gao, J. Song, J. Org. Chem., 2020, 85,
2733-2742.
A nickel-catalyzed sequential dehydrogenation and condensation process enables a
sustainable synthesis of a wide range of polysubstituted quinolines from
α-2-aminoaryl alcohols. This strategy allows the use of both primary as well as
secondary α-2-aminoaryl alcohols in combination with either ketones or secondary
alcohols for desired product formation.
S. Das, D. Maiti, S. D. Sarkar, J. Org. Chem., 2018, 83,
2309-2316.
An Ir-catalyzed synthesis of functionalized quinolines from 2-aminobenzyl
alcohols and α,β-unsaturated ketones tolerates a broad range of functional
groups, offers high efficiency, is environmentally benign, and can be performed
on a gram scale. Alkali is essential for the high selectivities of this
catalytic system.
N. Luo, H. Shui, Y. Zhong, J. Huang, R. Luo, Synthesis, 2021, 53,
4516-4524.
By employing α-chlorodiazirines as thermal precursors to the corresponding
chlorocarbenes, the traditional haloform-based protocol central to the parent
Ciamician-Dennstedt rearrangement can be modified to directly afford
3-(hetero)arylpyridines and quinolines. Chlorodiazirines are conveniently
prepared in a single step by oxidation of commercially available amidinium salts.
. D. Dherange, P. Q. Kelly, J. P. Liles, M. S. Sigman, M. D. Levin, J. Am. Chem. Soc.,
2021, 143, 11337-11344.
COOH as a weakly
coordinating and traceless directing group is essential for a synthesis of diverse polysubstituted quinolines from readily
available acrylic acids and anthranils. Diverse polysubstituted
quinolines were obtained under mild reaction conditions with simple H2O and CO2
as byproducts.
Y. Gao, J. Nie, Y. Li, X. Li, Q. Chen, Y. Huo, X.-Q. Hu,
Org. Lett., 2020, 22, 2600-2605.
Autoxidation of organoboronic acids using 1 atm of O2 enables a
simple, clean, and green carbon-carbon bond formation to provide structurally
diverse heteroaromatics with medicinally privileged scaffolds.
L. Zhang, Z.-Q. Liu, Org. Lett.,
2017, 19, 6594-9567.
The use of K2S2O8 and DMSO enables an efficient and transition-metal-free synthesis of
4-arylquinolines from readily available aryl alkynes and anilines with a
diverse range of substitution patterns. DMSO acts as one carbon source, thus
providing a highly atom-economical and environmentally benign approach for the
synthesis of 4-arylquinolines.
M. Phanindrudu, S. B. Wakade, D. K. Tiwari,
P. R. Likhar, D. K. Tiwari, J. Org. Chem., 2018, 83,
9137-9143.
A simple and efficient method enables a direct synthesis of substituted
quinolines from anilines and aldehydes through C-H functionalization, C-C/C-N
bond formation, and C-C bond cleavage in the presence of air as an oxidant.
R. Yan, X. Liu, C. Pan, X. Zhou, X. Li, X. Kang, G. Huang, Org. Lett., 2013,
15, 4876-4879.
An oxidative annulation involving anilines, aryl ketones, and DMSO as a
methine (=CH−) equivalent promoted by K2S2O8
provides 4-arylquinolines, whereas activation of acetophenone-formamide
conjugates enables the synthesis of 4-arylpyrimidines.
S. D. Jadhav, A. Singh, Org. Lett.,
2017, 19, 5673-5676.
A highly efficient and regioselective Co(III)-catalyzed C-H activation/cyclization
of simple, cheap, and easily available anilines with alkynes enables a direct
synthesis of a broad range of privileged quinolines. In this reaction, DMSO
serves both as the solvent and a C1 building block.
X. Xu, Y. Yang, X. Zhang, W. Yi, Org. Lett.,
2018, 20, 566-569.
[4 + 2] Cycloaddition of azadienes (in situ generated from 2-aminobenzyl alcohol)
and terminal alkynes enables a highly efficient metal and protection-free
approach for the regioselective synthesis of C-3-functionalized quinolines,
which are difficult to access.
R. K. Saunthwal, M. Patel, A. K. Verma, J. Org. Chem.,
2016, 81, 6563-6572.
Singlet diradical Ni(II) featuring two antiferromagnetically coupled singlet
diradical diamine type ligands catalyzes simple, straightforward, and atom
economic syntheses of quinolines, 2-aminoquinolines, and quinazolines in good
yields via biomimetic dehydrogenative condensation/coupling reactions.
G. Chakraborty, R. Sikari, S. Das, R. Mondal, S. Sinha, S. Banerjee, N. D. Paul, J. Org. Chem., 2019, 84,
2626-2641.
An annulation between 2-aminobenzyl alcohols, benzaldehydes, and DMSO
provides quinolines. Interestingly, introducing substituent groups to the
α-position of sulfoxides resulted in the interchange of the positions between
benzaldehydes and sulfoxides in the product quinolines.
T. Yang, Z.-w. Nie, M.-d. Su, H. Li, W.-p. Luo, Q. Liu, C.-C. Guo, J. Org. Chem., 2021, 86,
15232-15241.
Selective addition of radicals to isonitriles enables a general route for the
preparation of N-heteroaromatics. This method utilizes alkenes as
synthetic equivalents of alkynes by coupling homoallylic ring expansion to yield
the formal 6-endo products with aromatization via stereoelectronically
assisted C-C bond scission.
C. J. Evoniuk, G. dos Passos Gomes, M. Ly, F. D. White, I. V. Alabugin, J. Org. Chem.,
2017, 82, 4265-4278.
Benzylamine as the nucleophilic catalyst enables an on-water synthesis of 2-substituted quinolines
in excellent yields from 2-aminochalcone
derivatives. This protocol offers simple operation, broad substrate scope,
good functional group tolerance, easy product isolation by simple filtration, recycling of the
catalyst, and gram-scale synthesis.
S. Y. Lee, C.-H. Cheon, J. Org. Chem., 2018, 83,
13036-13044.
Quinolines can be synthesized from Δ2-isoxazolines under
reductive conditions. The reductive cyclization to quinolines is achieved in the
presence of iron or sodium dithionite under metal-free conditions.
P. Kamath, R. C. Viner, S. C. Smith, M. Lal,
Synlett, 2017, 28, 1341-1345.
In a new benzylation protocol, various 1,2,3,4-tetrahydroquinolines were
efficiently converted in combination with aryl aldehydes into β-benzylated
quinolines by employing readily available [RuCl2(p-cymene)]2
as a catalyst and O2 as a sole green oxidant. This step- and
atom-economic reaction offers excellent functional group tolerance and
chemoselectivity.
Z. Tan, H. Jiang, M. Zhang, Org. Lett.,
2016, 18, 3154-3157.
A highly chemoselective domino condensation/aza-Prins cyclization/retro-aldol
between 2-alkenylanilines and β-dicarbonyl compounds provides a large variety of
valuable 2-substituted quinolines in good yields. This metal-free reaction
tolerates a broad range of functional groups and can even be simpliefied into a
three component domino reaction.
J. Nan, P. Chen, Y. Zhang, Y. Yin, B. Wang, Y. Ma, J. Org. Chem., 2020, 85, 14042-14054.
In the presence of [Cp*Ir(6,6'-(OH)2bpy)(H2O)][OTf]2,
an acceptorless dehydrogenative cyclization of o-aminobenzyl alcohols
with ketones provided quinolines in high yields.
R. Wang, H. Fan, W. Zhao, F. Li, Org. Lett.,
2016, 18, 3558-3561.
A practicable quinoline synthesis from aniline and two amino acids provides a
wide range of quinolines with high efficiency and diversity including
pharmaceutical derivatives, photochemical active compounds, and challenging
scaffolds. Mechanistic studies revealed that I2 promotes
decarboxylation, oxidative deamination, and selective formation of new C-N and
C-C bonds.
J.-C. Xiang, Z.-X. Wang, Y. Cheng, S.-Q. Xia, M. Wang, B.-C. Tang, Y.-D. Wu,
A.-X. Wu, J. Org. Chem.,
2017, 82, 9210-9216.
A three-component cascade annulation of readily available aryl diazonium salts,
nitriles, and alkynes enables an efficient, additive-free, and rapid synthesis
of multiply substituted quinolines in good yields. Various aryl diazonium salts,
nitriles, and alkynes can participate in this transformation.
H. Wang, Q. Xu, S. Shen, S. Yu, J. Org. Chem.,
2017, 82, 770-775.
An oxidative annulation of o-allylanilines provides 2,4-diarylquinolines
in good yields in the presence of chloranil as recyclable oxidant. Furthermore,
a one-pot access to 2,4-diarylquinolines from easily available anilines and
1,3-diarylpropenes is described.
D. Cheng, X. Yan, J. Shen, Y. Pu, X. Xu, J. Yan, Synthesis, 2020, 52,
1833-1840.
A hydride Mn(I) PNP pincer complex catalyzes environmentally benign,
sustainable, and practical syntheses of substituted quinolines and pyrimidines
using combinations of 2-aminobenzyl alcohols and alcohols as well as benzamidine
and two different alcohols, respectively. The reactions proceed with high atom
efficiency via a sequence of dehydrogenation and condensation steps in very good
isolated yields.
M. Mastalir, M. Glatz, E. Pittenauer, G. Allmaier, K. Kirchner, J. Am. Chem. Soc., 2016,
138, 15303-15306.
An efficient palladium(II)-catalyzed C-C coupling/cyclization reaction by
directed C-H activation of benzamidine and terminal alkynes enables a practical
and high-yielding synthesis of quinolines, in which the C-N bond acts as an
internal oxidant. When using benzamidine with an ortho-methyl substituent,
a [1,5]-hydrogen migration followed by a Diels-Alder reaction with terminal
alkynes take place.
X. Zhang, X. Xu, Y. Wu, Z. Wang, L. Yu, Q. Zhao, F. Shi,
Synlett, 2015, 26, 1885-1889.
An iron-catalyzed intermolecular [4 + 2] cyclization of arylnitrones with
geminal-substituted vinyl acetates enables the synthesis of 2,4-disubstituted
quinolines in good yields with good functional group compatibilities.
Preliminary mechanistic studies suggest an iron-catalyzed C-H activation process.
M. Zhong, S. Sun, J. Cheng, Y. Shao, J. Org. Chem.,
2016, 81, 10825-10831.
In an efficient cascade copper-catalyzed intermolecular Ullmann-type C-N
coupling/enamine condensation reaction, ortho-acylanilines and alkenyl
iodides are converted to multisubstituted quinolines in very good yields.
J. Zheng, L. Huang, C. Huang, W. Wu, H. Jiang, J. Org. Chem.,
2015,
80, 1235-1242.
A regioselective 6-endo-trig intramolecular oxidative cyclization
enabled an efficient synthesis of 2-aryl 4-substituted quinolines from stable
and readily available o-cinnamylanilines with KOtBu as a mediator
and DMSO as an oxidant at rt. The reaction showed a broad substrate scope with
very good yields.
M. Rehan, G. Hazra, P. Ghorai, Org. Lett.,
2015,
17, 1668-1671.
A silver-catalyzed sequential formation of two C-C bonds enabels the
construction of a series of polysubstituted quinolines from anilines, aldehydes,
and alcohols under mild conditions. The transformation is effective for a broad
range of substrates, including aliphatic alcohols, arylalkanols, cycloalkanols,
and ethylene glycol.
X. Zhang, W. Liu, R. Sun, X. Xu, Z. Wang, Y. Yan,
Synlett, 2016, 27, 1563-1568.
A tandem reaction consisting of a [IrCp*Cl2]2/KOH
catalyzed isomerization/cyclization of allylic alcohols with 2-aminobenzyl
alcohol enables the synthesis of quinolines. Secondary and primary allylic
alcohols afford differently substituted quinoline derivatives in good yields.
S.-j. Chen, G.-p. Lu, C. Cai, Synthesis, 2015, 47,
976-984.
A series of 2,4-disubstituted quinolines were easily prepared through a
one-pot reaction of structurally diverse 2-aminoaryl ketones with various
arylacetylenes in the presence of K5CoW12O40 •
3 H2O as a reusable and environmentally benign catalyst under
microwave irradiation and solvent-free conditions.
I. Mohammadpoor-Baltork, S. Tangestaninejad, M. Moghadam, V. Mirkhani, S.
Anvar, A. Mirjafari, Synlett, 2010,
3104-3112.
An eco-friendly method allows the synthesis of 2,4-disubstituted quinolines via
Meyer-Schuster rearrangement of 2-aminoaryl ketones and phenylacetylenes in the
presence of a catalytic amount of zinc trifluoromethanesulfonate in the ionic
liquid [hmim]PF6. The ionic liquid can be recycled.
R. Sarma, D. Prajapati, Synlett, 2008,
3001-3005.
A facile and efficient iron-catalyzed intramolecular allylic amination of
2-aminophenyl-1-en-3-ols proceeded smoothly to afford 1,2-dihydroquinoline and quinoline derivatives under mild reaction conditions with
good yields.
Z. Wang, S. Li, B. Wu, Y. Wang, X. Sun, J. Org. Chem., 2012,
77, 8615-8620.
A cross-coupling of unprotected ortho-bromoanilines with a wide range of
cyclopropanols yields quinolines in a single operation via an intramolecular
condensation and palladium-catalyzed oxidation sequence. Deuterium-labeling
experiments provide direct evidence of a second equivalent of bromoaniline
serving as the terminal oxidant.
A. Nikolaev, N. Nithiy, A. Orellana,
Synlett, 2014, 25, 2301-2305.
An electrochemical hydrogen atom transfer (HAT) strategy enables a C(sp2)-H
formylation of electron-deficient quinolines and isoquinolines using methanol as
a formyl source with a catalytic amount of N-hydroxyphthalimide (NHPI) as
hydrogen atom transfer (HAT) catalyst. This transition-metal and oxidant-free
method could also be applied to the direct C(sp2)-H acetylation or
propionylation.
Y. Liao, C. Jiang, C. Qiang, P. Liu, P. Sun, Org. Lett., 2023, 25,
7327-7331.
An efficient one-pot procedure allows the preparation of substituted quinolines
from activated acetylenes and o-tosylamidocarbonyl compounds under
base-catalyzed, mild conditions. The generation of a β-phosphonium enoate
α-vinyl anion in situ is followed by Michael addition of the deprotonated
tosylamides and subsequent rapid aldol cyclization. Detosylation of the
dihydroquinoline intermediates occurred readily in the presence of aqueous HCl.
S. Khong, O. Kwon, J. Org. Chem., 2012,
77, 8257-8267.
An unprecedented synthesis of aromatic ring annulated pyridines from suitably
substituted primary allylamines via intramolecular electrophilic aromatic
cyclization is mediated by molecular iodine under mild conditions.
H. Batchu, S. Bhattacharyya, S. Batra, Org. Lett., 2012,
14, 6330-6333.
The use of vinyl ethers as robust, inexpensive acetyl sources enables a mild,
operationally simple Minisci C-H acetylation of N-heteroarenes. The
reaction does not require a catalyst or high temperature and is therefore
significantly more sustainable than previously reported methods in terms of cost,
reagent toxicity, and waste generation.
J. Dong, J. Liu, H. Song, Y. Liu, Q. Wang, Org. Lett., 2021, 23,
4374-4378.
A highly efficient I2-promoted formal [4 + 2] cycloaddition enables
the synthesis of 2-acylquinolines from methyl ketones and arylamines using
1,4-dithane-2,5-diol as an ethylene surrogate. This reaction occurred via an
iodination/Kornblum oxidation/Povarov/aromatization sequence with an
important role of the arylamine substrate in promoting the reaction.
X. Wu, X. Geng, P. Zhao, J. Zhang, X. Gong, Y.-d. Wu, A.-x. Wu, Org. Lett.,
2017, 19, 1550-1553.
The
electrophilic/nucleophilic bias of free radicals can be adjusted by altering the
reaction conditions. Photocatalytically generated imine radicals produce 3,4-disubstituted
quinolines via a novel rearrangement in the presence of an inorganic base.
Alternatively, in the presence of an organic base, they react to furnish
2,3-disubstituted quinolines.
R. Jiao, X. Ren, X. Li, S. Sun, H. Zhu, B. Lin, H. Hua, D. Li, X. He, Org. Lett., 2024,
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51-56.
Iron(II) phthalocyanine catalyzes a photo-thermo-mechanochemical synthesis of
quinolines. This solvent-free transformation features a cost-efficient catalytic
system and operational simplicity, and shows good substrate tolerance, providing
a green alternative to existing thermal approaches.
L. Liu, J. Lin, M. Pang, H. Jin, X. Yu, S. Wang, Org. Lett.,
2022, 24, 1146-1151.
Visible light induces a convenient radical cascade
acylation/cyclization/aromatization of N-propargyl aromatic amines and
acyl oxime esters for the construction of 3-acylated quinolines. This approach
uses acyl oxime esters as the precursor of acyl radicals as well as acylation
reagents, Eosin Y as the photocatalyst, and acetonitrile as the solvent.
M. Zhang, S. Wu, L. Wang, Z. Xia, K. Kuang, Q. Xu, F. Zhao, N. Zhou, J. Org. Chem., 2022, 87,
10277-10284.
A synergistic I2/amine promoted formal [4 + 2] cycloaddition of
methyl ketones, arylamines, and aryl(alkyl)acetaldehydes provides various
2-acyl-3-aryl(alkyl)quinolines via an iodination/Kornblum oxidation/Povarov/aromatization
sequence. Notably, the arylamine reactants also acted as indispensable catalysts
to promote enamine formation.
X. Geng, X. Wu, P. Zhao, J. Zhang, Y.-D. Wu, A.-X. Wu, Org. Lett.,
2017, 19, 4179-4182.
A ruthenium-catalyzed [5 + 1] annulation of 2-alkenylanilines with sulfoxonium
ylides provides highly functionalized quinolines with good yields and excellent
functional group tolerance.
P. Chen, J. Nan, Y. Hu, Q. Ma, Y. Ma,
Org. Lett., 2019, 21, 4812-4815.
Synergistic control of the temperature and amount of catalyst enables a
divergent synthesis of N-arylenaminones and 3-aroylquinolines from
2-aminoaryl ketones and N,N-dimethylenaminones in the presence of
4-toluenesulfonic acid. The protocols offers mild conditions, good
functional-group tolerance, operational simplicity, and excellent yields.
P. Zhou, B. Hu, K. Rao, L. Li, J. Yang, C. Gao, F. Wang, F. Yu,
Synlett, 2018, 29, 519-524.
A one-pot reaction cascade reaction enables a transition-metal-free construction
of functionalized quinolines from readily available acetophenones and anthranils.
The reaction involves in situ generation of α,β-unsaturated ketones from the
acetophenone via one-carbon homologation by DMSO followed by the aza-Michael
addition of anthranils and subsequent annulation. DMSO acts not only as solvent
but also as one carbon source.
S. B. Wakade, D. K. Tiwari, P. S. K. P. Ganesh, M. Phanindrudu, P. R. Likhar, D.
K. Tiwari, Org. Lett.,
2017, 19, 4948-4951.
A palladium-catalyzed Heck reaction enables an efficient synthesis of
2,3-disubstituted quinoline derivatives from easily accessible (het)aryl-substituted
Morita-Baylis-Hillman adducts via α-benzyl β-keto ester derivatives that can
cyclize into the corresponding quinolines in good yields.
K. Selvakumar, K. A. P. Lingam, R. V. L. Varma, V. Vijayabaskar,
Synlett, 2015, 26, 646-650.
A Pd-catalyzed oxidative cyclization of o-vinylanilines and alkynes in
the presence of molecular oxygen enables the construction of 2,3-disubstituted
quinolines via intermolecular amination of alkyne, insertion of the olefin, and
oxidative cleavage of a C-C bond.
J. Zheng, T. Li, L. Huang, W. Wu, J. Li, H. Jiang, Org. Lett.,
2016, 18, 3514-3517.
A visible-light induced photocatalytic aerobic oxidative dehydrogenative
coupling/aromatization tandem reaction of glycine esters with unactivated
alkenes provides quinoline derivatives in good yield under mild and
operationally simple reaction conditions.
X. Yang, L. Li, Y. Li, Y. Zhang, J. Org. Chem.,
2016, 81, 12433-12442.
While copper-catalyzed 6-endo-dig cyclization of
propargylamines generates 2-substitued quinoline-4-carboxylates, iron-promoted
cascade amino Claisen rearrangement, aromatization, and aza-Michael addition
affords diverse 2-substituted indole-3-carboxylates. The reactions offer
excellent selectivity, broad functional group tolerance, and mild conditions.
H. Zhang, Y. Zi, C. Cao, W. Huang, A. Jiang, C. Lu, J. He, Y. Tang, Z.-G. Wu, Org. Lett., 2023, 25,
9030-9035.
A highly efficient molecular iodine mediated formal [3 + 2 + 1] cycloaddition
reaction enables the direct synthesis of substituted quinolines from methyl
ketones, arylamines, and styrenes. A self-sequenced iodination/Kornblum
oxidation/Povarov/aromatization mechanism has been proposed.
Q. Gao, S. Liu, X. Wu, A. Wu, Org. Lett.,
2014,
16, 4582-4585.
A domino C-H functionalization of glycine derivatives for the production of a
series of quinolines was achieved under catalytic radical cation salt induced
conditions. A mechanism is proposed, that includes a peroxyl radical cation,
which is generated by the coupling between O2 and TBPA+•.
X. Jia, F. Peng, C. Qing, C. Huo, X. Wang, Org. Lett., 2012,
14, 4030-4033.
An iron-promoted tandem reaction of anilines with styrene oxides via C-C
cleavage and C-H activation utilizes inexpensive FeCl3 as promoter
and is suitable for forming various 3-arylquinolines from simple and readily
available starting materials.
Y. Zhang, M. Wang, P. Li, L. Wang, Org. Lett., 2012,
14, 2206-2209.
An efficient single-step approach toward the synthesis of 2-alkylquinolines is
mediated by a Lewis acid through [3 + 3] annulation reaction between
3-ethoxycyclobutanones and aromatic amines. Various multisubstituted
2-alkylquinoline derivatives were prepared regioselectively at room temperature.
G. Shan, X. Sun, Q. Xia, Y. Rao, Org. Lett., 2011,
13, 5770-5773.
An environmentally friendly and highly efficient procedure gives
2,4-disubstituted quinoline derivatives by a simple alkynylation-cyclization
reaction of 2-aminoaryl ketones with phenylacetylenes in the presence of
indium(III) trifluoromethanesulfonate In(OTf)3 under microwave
irradiation and solvent-free conditions. The catalyst can be reused.
K. C. Lekhok, D. Prajapati, R. C. Boruah, Synlett, 2008,
655-658.
A cooperative catalytic system, consisting of CuI and pyrrolidine enables an
efficient synthesis of 2-substituted quinolines. A combination of both catalysts
is necessary; the use of either catalyst alone does not give the product.
N. T. Patil, V. S. Raut, J. Org. Chem., 2010,
75, 6961-6964.
A three-component reaction of nitroarenes, aldehydes, and phenylacetylene in the
presence of indium in dilute hydrochloric acid produces quinoline derivatives
under reflux. The conversion involves reduction of the nitroarenes to anilines
followed by coupling of the anilines, aldehydes, and phenylacetylene, followed
by cyclization of the resulting species and dehydrogenation of the cyclic
intermediates.
B. Das, P. Jangili, J. Kashanna, R. A. Kumar, Synthesis, 2011,
3267-3270.
A straightforward and efficient Yb(OTf)3 catalyzed three-component
reaction of aldehydes, alkynes, and amines under microwave irradiation in an
ionic liquid provides 2,4-disubstituted quinolines in excellent yield under mild
reaction condition. The catalyst can be recycled up to four times.
A. Kumar, V. K. Rao, Synlett, 2011,
2157-2162.
A Fe(acac)3/TBAOH-catalyzed three-component
coupling-cycloisomerization reaction of aldehydes, terminal alkynes, and amines
provides a diverse range of heterocyclic compounds such as aminoindolizines and
quinoline derivatives in good yields.
S. S. Patil, S. V. Patil, V. D. Bobade, Synlett, 2011,
2379-2383.
A modified Larock method enables a one-pot synthesis of substituted quinolines
via a Heck reaction of 2-bromoanilines and allylic alcohols followed by
dehydrogenation with diisopropyl azodicarboxylate (DIAD).
M. T. Stone, Org. Lett., 2011,
13, 2326-2329.
An efficient and regioselective alkenylation of azaheterocycle N-oxides with
alkenes is catalyzed by iodine under metal- and external oxidant-free reaction
conditions to provide various (E)-2-styrylazaheterocycles in good yields.
The N-oxide group plays a dual role as both the directing group and an internal
oxidant.
Z. Zhang, C. Pi, H. Tong, X. Cui, Y. Wu, Org. Lett.,
2017, 19, 440-443.
A novel copper-catalyzed [5 + 1] annulation of 2-ethynylanilines with an N,O-acetal
gives quinoline derivatives with an ester substituent on the 2-position. A
combination of CuBr2 and trifluoroacetic acid (TFA) promotes a [5 +
1] annulation of 2-ethynylaniline with ethyl glyoxylatein the presence of
piperidine.
N. Sakai, K. Tamura, K. Shimamura, R. Ikeda, T. Konakahara, Org. Lett., 2012,
14, 836-839.
Treatment of N-tosyl-2-propynylamines with diphenyliodonium triflate in
the presence of K3PO4 and a catalytic amount of CuCl at
room temperature followed by N-iodosuccinimide and BF3·OEt2
at 0°C, and then NaOH in methanol solution provided 3-iodo-4-arylquinolines.
Products underwent various cross-coupling reactions and were smoothly
dehalogenated with zinc.
T. Sasaki, K. Moriyama, H. Togo, J. Org. Chem.,
2017, 82, 11727-11734.
An electrophilic cyclization of alkynyl imines provides polysubstituted
3-haloquinolines using CuX-activated N-halosuccinimdes (NXS) as
electrophiles. The NXS/CuX system is more active than single NXS and can be
applied in the electrophilic cyclization of electron-deficient substrates.
L. Liu, D. Chen, J. Yao, Q. Zong, J. Wang, H. Zhou, J. Org. Chem.,
2017, 82, 4625-4630.
Highly substituted 3-iodoquinolines bearing different alkyl and aryl moieties
can be synthesized in good yields by a regioselective 6-endo-dig iodocyclization
of 2-tosylaminophenylprop-1-yn-3-ols with molecular iodine under mild conditions.
The resulting 3-iodoquinolines can be further functionalized by various coupling
reactions.
S. Ali, H.-T. Zhu, X.-F. Xia, K.-G. Ji, Y.-F. Yang, X.-R. Song, Y.-M. Liang, Org. Lett., 2011,
13, 2598-2601.
Upon photoirradiation of o-alkynylaryl isocyanides in the presence of
iodine, an intramolecular cyclization affords the corresponding
2,4-diiodoquinolines in good yields. 2,4-Diiodoquinolines can be employed in
regioselective transition metal-catalyzed cross-coupling reactions.
T. Mitamura, A. Ogawa, X. Pan, J. Org. Chem., 2011,
76, 1163-1166.
A Pd-catalyzed Wacker-type oxidative cyclization under air allows the
construction of 2-methylquinolines in good yields under mild conditions.
Z. Zhang, J. Tang, Z. Wang, Org. Lett., 2008,
10, 173-175.
A direct reaction between 2-aminobenzylic alcohol derivatives and either ketones
or alcohols in the presence of a base and benzophenone as hydride scavenger
allows the synthesis of polysubstituted quinolines without any transition-metal
catalyst.
R. Martínez, D. J. Ramón, M. Yus, J. Org. Chem., 2008,
73, 9778-9780.
An efficient and convenient nickel-catalyzed cyclization of 2-iodoanilines
with alkynyl aryl ketones gives 2,4-disubstituted quinolines. Naturally
occurring quinoline derivatives have been prepared in good yields. The
mechanism is discussed.
R. P. Korivi, C.-H. Cheng, J. Org. Chem., 2006, 71, 7079-7082.
A direct convergent two-component synthesis of quinolines from α,β-unsaturated
ketones and o-aminophenylboronic acid derivatives is regiocomplementary
to the traditional Skraup-Doebner-Von Miller synthesis and proceeds under basic
rather than strongly acidic conditions.
J. Horn, S. P. Marsden, A. Nelson, D. House, G. G. Weingarten, Org. Lett.,
2008,
10, 4117-4120.
An efficient reductive cyclization of o-nitrocinnamoyl compounds was
achieved by employing Hantzsch 1,4-dihydropyridine diethyl ester as a biomimetic
reducing agent in the presence of catalytic palladium on carbon. This approach
was successfully applied to the synthesis of substituted quinolines.
R.-G. Xing, Y.-N. Li, Q. Liu, Y.-F. Han, X. Wei, J. Li, B. Zhou, Synthesis, 2011,
2066-2072.
Reduction of secondary and tertiary o-nitrophenyl propargyl alcohols followed
by acid-catalyzed Meyer-Schuster rearrangement gave 2-substituted and
2,4-disubstituted quinolines, respectively in good yields.
M. J. Sandelier, P. DeShong, Org. Lett., 2007,
9, 3209-3212.
A one-pot dehydrogenative Povarov/oxidation tandem reaction of N-alkyl anilines
with mono- and 1,2-disubstituted aryl and alkyl olefins enables the synthesis of
a various substituted quinolines. The simple protocol uses cheap and benign
iron(III)chloride as the Lewis acid catalyst and a TEMPO oxoammonium salt as a
nontoxic, mild, efficient oxidant.
H. Richter, O. G. Mancheño, Org. Lett., 2011,
13, 6066-6069.
A domino reaction of benzimidoyl chlorides with 1,6-enynes gives quinoline
derivatives via palladium-catalyzed Sonogashira coupling and subsequent
cyclization. The reaction conditions and the scope of the process are examined,
and a plausible mechanism is proposed. The procedure is simple, rapid, and
general, and the substrates are readily available.
G.-L. Gao, Y.-N. Niu, Z.-Y. Yan, H.-L. Wang, G.-W. Wang, A. Shaukat, Y.-M. Liang, J. Org. Chem., 2010,
75, 1305-1308.
The intramolecular cyclization of 1-azido-2-(2-propynyl)benzene proceeds
smoothly in the presence of electrophilic reagents in CH3NO2
at room temperature or in the presence of catalytic amounts of AuCl3/AgNTf2
in THF at 100°C to afford the corresponding quinolines 2 in good to high yields.
Z. Huo, I. D. Gridnev, Y. Yamamoto, J. Org. Chem., 2010,
75, 1266-1270.
4-Aryl and 4-vinyl quinolines were prepared via a sequential procedure involving
regioselective rhodium-catalyzed hydroarylation/hydrovinylation of
β-(2-aminophenyl)-α,β-ynones with arylboronic acids or potassium aryl and vinyl
trifluoroborates, followed by nucleophilic attack of the amino group onto the
carbonyl.
G. Abbiati, A. Arcadi, F. Marinelli, E. Rossi, M. Verdecchia, Synlett, 2006,
3218-3224.
A simple, efficient and convenient copper-catalyzed method allows the synthesis
of quinoline-2-carboxylate derivatives through sequential intermolecular
addition of alkynes onto imines and subsequent intramolecular ring closure by
arylation at room temperature.
H. Huang, H. Jiang, K. Chen, H. Liu, J. Org. Chem., 2009,
74, 5476-5480.
A copper-catalyzed tandem annulation of alkynyl imines with diazo compounds
enables an efficient synthesis of a broad range of C4-functionalized quinolines
in good yields via in situ formation of allene and intramolecular
electrocyclization. The reaction offers high efficiency, mild reaction
conditions, easy operation, and broad functional-group tolerance.
R. Zhu, G. Cheng, C. Jia, L. Xue, X. Cui, J. Org. Chem.,
2016, 81, 7539-7544.
An efficient [2 + 1 + 3] cyclization reaction of aryl methyl ketones, arylamines, and
1,3-dicarbonyl compounds provides 2-aryl-4-quinolinecarboxylates in good yields
under mild conditions. This metal-free process achieved a C-C bond cleavage of 1,3-dicarbonyl compounds
for use as a C1
synthon.
Y. Zhou, P. Zhao, L.-S. Wang, X.-X. Yu, C. Huang, Y. D. Wu, A.-X. Wu, Org. Lett., 2021, 23, 6461-6465.
A highly efficient I2-catalyzed Povarov-type reaction of methyl
ketones, arylamines, and α-ketoesters provides substituted quinolones in very
good yields. The convenient procedure offers good functional group compatibility.
Q. Gao, S. Liu, X. Wu, J. Zhang, A. Wu, J. Org. Chem.,
2015,
80, 5984-5991.
Cu-catalyzed aerobic cyclization of N-(2-alkynylaryl)enamine carboxylates
via intramolecular carbo-oxygenation of alkynes gives highly substituted
quinolines. This strategy was further applied for N-alkynylamidines
leading to imidazole and quinazoline derivatives.
K. K. Toh, S. Sanjaya, S. Sahnoun, S. Y. Chong, S. Chiba, Org. Lett., 2012,
14, 2290-2292.
An efficient Cu-catalyzed annulation reaction of ketone oxime acetates with
ortho-trifluoroacetyl anilines provides 4-trifluoromethyl quinolines in
very good yields under redox-neutral conditions.
Z.-H. Wang, L.-W. Shen, P. Yang, Y. You, J.-Q. Zhao, W.-C. Yuan, J. Org. Chem., 2022, 87,
5804-5816.
A [5 + 1] cyclization of 2-vinylanilines with polyfluoroalkanoic acids as
both C1 synthons and fluoroalkyl building blocks under catalyst- and
additive-free conditions provides concise access to diverse 2-fluoroalkylated
quinolines in good yields with excellent functional group tolerance in high
yield on a gram scale.
J. Nan, Y. Hu, P. Chen, Y. Ma,
Org. Lett., 2019, 21, 1984-1988.
Pyridine N-oxides were converted to 2-aminopyridines in a one-pot fashion
using Ts2O-tBuNH2 followed by in situ deprotection
with TFA. The amination proceeded in high yields, excellent 2-/4-selectivity,
and with good functional group compatibility.
J. Yin, B. Xiang, M. H. Huffman, C. E. Raab, I. W. Davies, J. Org. Chem., 2007,
72, 4554-4557.
A sustainable synthesis of quinazoline and 2-aminoquinoline via acceptorless
dehydrogenative annulation is catalyzed by earth-abundant well-defined manganese
complexes bearing NNS ligands.
K. Das, A. Mondal, D. Pal, D. Srimani,
Org. Lett., 2019, 21, 3223-3227.
A palladium-catalyzed annulation of N-acyl-o-alkynylanilines
with isocyanides provides functionalized 2-aminoquinolines with high atom economy
via an
unconventional 6-endo-dig cyclization process. Further
investigations of the mechanism revealed that an intramolecular acyl
migration of the N-protecting groups is involved.
M. Li, J. Zheng, W. Hu, C. Li, J. Li, S. Fang, H. Jiang, W. Wu, Org. Lett.,
2018, 20, 7245-7248.
A [3+2] dipolar cycloaddition of azine N-oxide withs carbodiimides
provides 2-amino azines smoothly under simple heating conditions without any
transition metal catalyst, activator, base, and solvent. This transformation
demonstrates a broad substrate scope and produces CO2 as the only
co-product.
B. K. Sarmah, M. Konwar, A. Das, J. Org. Chem., 2021, 86,
10762-10772.
Mn(III) acetate as a mild one-electron oxidant promotes a radical process to
construct polysubstituted quinolin-3-amines from
2-(2-isocyanophenyl)acetonitriles and organoboron reagents. This method is
practical, mild, efficient, and offers good functional group compatibility.
S. Wang, J. Xu, Q. Song, Org. Lett., 2021, 23,
6789-6794.
A robust and regioselective palladium-catalyzed intermolecular aerobic oxidative
cyclization of 2-ethynylanilines with isocyanides enables the synthesis of
4-halo-2-aminoquinolines with good yields and broad substrates scope.
Furthermore, this process can be easily extended to synthesis of various 6H-indolo[2,3-b]quinolines
via an intramolecular Buchwald-Hartwig cross-coupling reaction in a two-step
one-pot manner.
B. Liu, H. Gao, Y. Yu, W. Wu, H. Jiang, J. Org. Chem., 2013,
78, 10319-10328.
A nucleophile-induced intramolecular cyclization of o-alkynylisocyanobenzenes
provides 2,3-disubstituted quinoline derivatives in high yields. In addition to
oxygen and nitrogen nucleophiles such as methanol and diethylamine, the
nucleophilic carbon of the enolate of malonate induced the cyclization
effectively.
M. Suginome, T. Fukuda, Y. Ito,
Org. Lett., 1999, 1, 1977-1979.
A [5+1]-cyclization of 2-vinylanilines with tetraalkylthiuram disulfides in
the presence of iodine and copper(II) triflate provides a variety of
2-aminoquinolines in very good yields. This facile one-step synthesis directly
employs readily available and low-cost thiurams as both a C1 synthon and a
nitrogen source.
J. Jiao, P. Wang, F. Xiao, Z. Zhang, Synlett, 2022,
33,
569-574.
An efficient intermolecular amidation of quinoline N-oxides with
sulfonamides in the presence of PhI(OAc)2 and PPh3
provides N-(quinolin-2-yl)sulfonamides in very good yields.
X. Yu, S. Yang, Y. Zhang, M. Guo, Y. Yamaoto, M. Bao, Org. Lett.,
2017, 19, 6088-6091.
In a ligand-free chromium(II)-catalyzed amination reaction of various N-heterocyclic
chlorides, CrCl2 regioselectively catalyzes the reaction of
chloropyridines, chloroquinolines, chloroisoquinolines, and chloroquinoxalines
with a broad range of magnesium amides in the presence of lithium chloride as
additive. The reactionse provide the desired aminated products in good yield.
A. K. Steib, S. Fernandez, O. M. Kuzmina, M. Corpet, C. Gosmini, P. Knochel,
Synlett, 2015, 26, 1049-1054.
A rapid synthesis of quinolines from 2-alkenylanilines involves an unexpected
DMAP-catalyzed cyclization of 2-alkenylanilines with di-tert-butyl
dicarbonate providing a series of tert-butyl quinolin-2-yl carbonates
with various functional groups in good yields under mild conditions. Furthermore,
the tert-butyl quinolin-2-yl carbonate can be easily converted into
corresponding quinolinones and 2-(pseudo)haloquinolines.
Y.-N. Huang, Y.-L. Li, J. Li, J. Deng, J. Org. Chem.,
2016,
81, 4645-4653.
An aerobic dehydrogenative aromatization strategy enables an atom and step
economic synthesis of 4-aminoquinolines. Unlike the well-known
palladium-catalyzed dehydrogenative aromatization of cyclohexanones with amines,
synergistic Pd/Cu catalysis is crucial for 2,3-dihydroquinolin-4(1H)-one
type of substrates to give the corresponding 4-aminoquinoline products in good
yields.
F. Chen, H. Geng, C. Li, J. Wang, B. Guo, L. Tang, Y.-Y. Yang, J. Org. Chem., 2023, 88,
15589-15596.
4-Aminoquinolines can be prepared in a three-step synthesis: A condensation of
substituted anthranilonitriles with 1,1,1-trichloro-4-ethoxybut-3-enone
proceeded efficiently either neat or in refluxing EtOH. Cyclization in
superacidic trifluoromethanesulfonic acid provided an unstable intermediate,
which upon treatment with NaOEt in ethanol, afforded the expected ethyl
4-aminoquinoline-3-carboxylates.
H. Lavrard, P. Larini, F. Popowycz, Org. Lett.,
2017, 19, 4203-4206.
A copper-catalyzed regiocontrolled three-component reaction of nitriles,
diaryliodoniums, and ynamides provides diversified 4-aminoquinolines. The
C7-substituted regioisomers were formed regioselectively when meta-substituted
phenyliodonium salts were used. [1,3] N-to-C rearrangement of the products to
quinolin-4-ylmethanesulfonamides and simultaneous deprotection of benzyl and
sulfonamide group are also reported.
K. H. Oh, J. G. Kim, J. K. Park, Org. Lett.,
2017, 19, 3994-3997.
A regiospecific, metal-free TMSOTf-catalyzed [4 + 2] annulation of ynamides
with β-(2-aminophenyl)-α,β-ynones provides 2-aminoquinolines in good yields
under mild conditions. This nonmetal catalytic system is suitable for the
synthesis of 3-alkyl substituted products, which have not been obtained by known
methods.
C. Qi, X. Shen, W. Fang, J. Chang, X.-N. Wang, Org. Lett., 2024,
26, 3503-3508.