Synthesis of N-Heterocycles
| Synthesis of | |||
 benzo-fused N-Heterocycles |
Related: Substituted N-Heterocycles |
||
 Cyclic amines |
 Lactams |
 Sultams |
 Oxaziridines |
 Imidazolidones |
 Oxazolidinones |
 Hydantoins |
 1,3-Thiazolidine-2-thiones |
 Succinimides |
 Urazoles |
||
 Imidazolidines |
 4-Imidazolidinone |
 Pyrazolidines |
|
 Oxazolidines |
 Isoxazolidines |
||
 2H-Azirines |
 2-Azetines |
 Diazirines |
|
 3-Pyrrolines |
 2-Pyrrolines |
 1-Pyrrolines |
 Maleimides |
 3-Pyrrolin-2-ones |
 4-Pyrrolin-2-ones |
||
 2-Isoxazolines |
 3-Isoxazolines |
 4-Isoxazolines |
|
 2-Oxazolines |
 3-Oxazolines |
 2-Imidazolines |
 Thiazolines |
 Pyrazolines |
 3-Pyrazolines |
||
 Pyrroles |
 2H-Pyrroles |
||
 Imidazoles |
 Pyrazoles |
 3H-Pyrazoles |
|
 1,2,3-Triazoles |
 2H-1,2,3-triazoles |
 1H-1,2,4-Triazoles |
 4H-1,2,4-Triazoles |
 1H-Tetrazoles |
 2H-Tetrazoles |
||
 Imidazol-2-ones |
 Imidazol-5-ones |
 3H-1,2,4-triazol-3-ones |
|
 Oxazoles |
 Isoxazoles |
 1,3,4- Oxadiazoles |
 2-Oxazolones |
 1,2,4- Oxadiazoles |
 1,2,5- Oxadiazoles |
||
 Thiazoles |
 Isothiazoles |
||
 1,3,4- Thiadiazoles |
 1,2,4- Thiadiazoles |
 1,2,3- Thiadiazoles |
|
 Pyridines |
 Dihydro- pyridines |
 2,3-Dihydropyridines |
|
 1,2,3,4- Tetrahydropyridines |
 1,2,3,6- Tetrahydropyridines |
||
 3,4-Dihydro-2H-1,4-oxazines |
|||
 2-Pyridones |
|||
 Pyrazines |
 Pyrimidines |
 Pyridazines |
|
 1,3,5-Triazines |
 1,2,4-Triazines |
 1,2,3-Triazines |
|
 2,3-dihydro- 4-pyridones |
 Azepines |
Name Reactions
Recent Literature
A high-yielding, asymmetric synthesis of novel 4-formyl-1-(2- and
3-haloalkyl)azetidin-2-ones was developed as valuable starting materials for the
synthesis of different enantiomerically enriched bicyclic azetidin-2-ones, such
as piperazine, morpholine, and 1,4-diazepane annulated β-lactam derivatives.
W. Van Brabandt, M. Vanwalleghem, M. D'hooghe, N. De Kimpe, J. Org. Chem., 2006, 71, 7083-7086.
A [2 + 1 + 1] radical tandem cycloaddition of styrenes, arylamines, and tert-butyl
hydroperoxide enables a regioselective synthesis of polysubstituted
1,2-oxazetidines. TBHP was employed in this conversion not only as the oxidant
but also as the oxygen source.
W. Liu, C. Chen, P. Zhou, H. Tan, Org. Lett.,
2017, 19, 5830-5832.
An unprecedented (3+1) cyclization of α-nitrosostyrenes, generated in situ
from α-bromooximes, and N-tosyloxycarbamates provides structurally unique
2,3-dihydrodiazete N-oxides in good yields. These highly strained
four-membered ring structure products containing two nitrogen atoms can be
converted to diverse nitrogen-containing compounds.
L.-W. Shen, Z.-H. Wang, Y. You, J.-Q. Zhao, M.-Q. Zhou, W.-C. Yuan, Org. Lett.,
2022, 24, 1094-1099.
Bisphosphine-catalyzed mixed double-Michael reactions between amino-acid-derived
pronucleophiles as Michael donors and electron-deficient acetylenes as acceptors
afford β-amino carbonyl derivatives of oxazolidines, thiozolidines, and
pyrrolidines in excellent yields and with high diastereoselectivities under
operationally simple and mild conditions.
V. Sriramurthy, G. A. Barcan, O. Kwon, J. Am. Chem. Soc., 2007,
129, 12928-12929.
In situ generated aza-oxyallyl cation intermediates react with a variety of
carbonyl compounds via an efficient (3 + 2) cycloaddition to provide
4-oxazolidinones with good yields and diastereoselectivities.
A. Acharya, K. Montes, C. S. Jeffrey, Org. Lett.,
2016, 18, 6083-6085.
A silver oxide catalyzed [3 + 2] annulation of nitrones with isocyanides
provides a variety of 2,3,4-trisubstituted 1,2,4-oxadiazolidin-5-one derivatives
as single diastereomers in very good yields in the presence of oxygen as the
terminal oxidant.
X. Shen, A. Shatskiy, Y. Chen, M. D. Kärkäs, X.-S. Wang, J.-Q. Liu, J. Org. Chem., 2020, 85,
3560-3567.
A catalytic asymmetric ring-closing 1,5-C-H amination of sulfamoyl azides
provides chiral 1,2,5-thiadiazolidine-1,1-dioxides in up to 98% yield and up to
98% ee if the C-H bond is in a benzylic position. The reaction is catalyzed by a
recently introduced simple chiral ruthenium bis(oxazoline) (pybox) complex.
X. Nie, Z. Yan, S. Ivlev, E. Meggers, J. Org. Chem., 2021, 86,
750-761.
An efficient Pd-catalyzed formal [3 + 2] cycloaddition of vinylethylene
carbonates with isothiocyanates provides 1,3-oxazolidine-2-thione derivatives.
The zwitterionic π-allyl palladium intermediates formed in situ acted as the
three-membered synthons.
W. Xiong, S. Zhang, H. Li, Z. Zhang, T. Xu, J. Org. Chem., 2020, 85,
8773-8779.
Silver nitrate catalyzes a reaction of primary amines with methyl
α,α-disubstituted α-isocyanoacetates to provide 3,5,5-trisubstituted
imidazolones in very good yields via Ag-catalyzed insertion of the isocyano
group into the N-H bond of the amine followed by in situ lactamization. The
catalytic system also converts methyl 2-isocyanobenzoate and amines into
quinazolin-4-ones in excellent yields.
A. Clemenceau, Q. Wang, J. Zhu, Org. Lett.,
2017, 19, 4872-4875.
The reaction of tert-Butyl nitrite with terminal aryl alkenes provides
3-aryl-1,2,4-oxadiazol-5(4H)-ones via a biradical reaction intermediate.
Both of the nitrogen atoms and one oxygen originate from TBN, while the carbonyl
oxygen is from moisture.
P. Sau, A. Rakshit, T. Alam, H. J. Srivastava, B. K. Patel,
Org. Lett., 2019, 21, 4966-4970.
Pd(OAc)2 catalyzes a cyclization of propargylic alcohols with tert-butyl
nitrite at room temperature to provide 4-oxoisoxazoline N-oxides in good
yields under mild conditions.
K.-W. Feng, Y.-L. Ban, P.-F. Yuan, W.-L. Lei, Q. Liu, R. Fang,
Org. Lett., 2019, 21, 3131-3135.
A one-pot sequential N-acylation/dehydrative cyclization between ethyl
carbazate and N-acylbenzotriazoles in the presence of Ph3P-I2
as a dehydrating agent enables a convenient synthesis of 5-substituted-2-ethoxy-1,3,4-oxadiazoles. Subsequent treatment with a
stoichiometric amount of alkyl halides provides 3,5-disubstituted 1,3,4-oxadiazol-2(3H)-ones in
very good
yields.
S. Wet-osot, W. Phakhodee, M. Pattawarapan, J. Org. Chem.,
2017, 82, 9923-9929.
A potassium-carbonate-mediated [3 + 2]-cycloaddition reaction of
α-halohydroxamates with carbon disulfide provides functionalized rhodanine
derivatives in very good yields. The present methodology offers a wide substrate
scope as well as good functional group tolerance.
X. Lei, J. Feng, Q. Guo, C. Xu, J. Shi, Org. Lett.,
2022, 24, 2837-2841.
A visible light-promoted three-component tandem annulation of α-bromoesters,
amines, and aryl/alkyl isothiocyanates provides 2-iminothiazolidin-4-ones at
room temperature in the absence of metal and photocatalyst. This [1 + 2 + 2]
cyclization strategy offers broad substrate scope, excellent functional group
tolerance, mild reaction conditions, step-economy, and simple operation.
W. Guo, M. Zhao, W. Tan, L. Zheng, K. Tao, L. Liu, X. Wang, D. Chen, X. Fan, J. Org. Chem.,
2018, 83, 1402-1413.
An allenyl imide and alkynoates bearing good leaving groups are used as
ketene precursors in tandem conjugate addition-elimination reactions promoted by
nucleophilic phosphine catalysts. By utilizing thioamides as 1S,3N-bis-nucleophiles,
[3+3] and [3+2] annulations provide rapid access to 1,3-thiazin-4-ones and
5-alkenyl thiazolones in high yields, respectively.
Y.-H. Wang, Z.-N. Zhao, S. J. Kalita, Y.-Y. Huang, Org. Lett., 2021, 23,
8147-8152.
A convenient base-catalyzed three-component reaction between chalcones,
isothiocyanates, and elemental sulfur provides thiazole-2-thiones in very good
yields.
T. B. Nguyen, P. Retailleau, Org. Lett., 2021, 23,
5344-5348.
In a gold-catalyzed synthesis of bicyclic imidazoles, a highly electrophilic
α-imino gold carbene intermediate can react with a weakly nucleophilic nitrile,
which is used as the reaction solvent, to deliver the desired product rapidly in
an overall bimolecular [2 + 2 + 1] cycloaddition and in good yield. The
competing intramolecular azide-alkyne click reaction, although likely also
catalyzed by gold, is minimized by using AuCl3 as the catalyst.
Y. Xiao, L. Zhang, Org. Lett., 2012,
14, 4662-4665.
An iron-catalyzed [3 + 2] annulation from readily available oxime acetates with
vinyl azides enables the synthesis of 2,4-substituted 2H-imidazoles via
N-O/N-N bond cleavages and two C-N bond formations. This green reaction
involving oxime acetate as internal oxidant, acetic acid, and nitrogen as
byproducts can be performed under mild reaction conditions and needs no
additives or ligands.
Z. Zhu, X. Tang, J. Li, X. Li, W. Wu, G. Deng, H. Jiang, Org. Lett.,
2017, 19, 1370-1373.
Intramolecular addition of tosylureas to allenes is highly syn-/anti-diastereoselective
when employing a palladium or rhodium-based catalytic system and affords
1,3-cyclic ureas in excellent yields. The obtained
tetrahydropyrimidinones are easily deprotected and modified.
A. G. A. Geissler, K. R. Riesterer, B. Breit, Org. Lett., 2021, 23,
9168-9172.
A Pd-catalyzed α,β-desaturation of N-protected lactams provides
conjugated unsaturated counterparts under mildly acidic conditions at room
temperature. The reaction tolerates a wide range of functional groups and shows
reactivity complementary to that of prior desaturation methods. Lactams with
various ring sizes and substituents at different positions all reacted smoothly.
M. Chen. G. Dong, J. Am. Chem. Soc., 2017,
139, 7757-7760.
An oxidative relay Heck arylation reaction enables the construction of chiral
α,β-unsaturated δ-lactams, widely used as pharmacophores, in high yields and
excellent enantioselectivities. This strategy also allows facile access to
7-substituted α,β-unsaturated ε-lactam products and δ-lactams.
Q. Yuan, M. S. Sigman, J. Am. Chem. Soc.,
2018,
140, 6527-6530.
An N-heterocyclic carbene-catalyzed oxidative LUMO activation of the β-carbons of
saturated carboxylic esters enables an efficient asymmetric access to lactams
and lactones. The method introduces functional groups at the typically inert
β-sp3 carbons of saturated esters. The use of HOBt as an additive
improves both yields and enantioselectivities of the reactions.
B. Liu, W. Wang, R. Huang, J. Yan, J. Wu, W. Xue, S. Yang, Z. Jin, Y. R. Chi, Org. Lett.,
2018, 20, 260-263.
A Pd-catalyzed arylation of aza-Achmatowicz rearrangement products
with arylboronic acids provides 2-aryldihydropyridinones
for facile synthesis of highly functionalized 2-arylpiperidines. Key to this
arylation is the use of non-phosphine-ligand palladium precatalyst. The utility of
2-aryldihydropyridinones is illustrated by the synthesis of a small collection
of 2-arylpiperidines.
G. Zhao, D. P. Canterbury, A. P. Taylor, X. Cheng, P. Mikochik, S. W. Bagley,
R. Tong,
Org. Lett., 2020, 22, 458-463.
Fused bicyclic imidazole rings have been prepared in good yields by a
sequence of the van Leusen three-component reaction and the ring-closing
metathesis reaction.
V. Gracias, A. F. Gasiecki, S. W. Djuric, Org. Lett., 2005, 7, 3183-3186.
Palladium-catalyzed alkene carboamination reactions between acyclic N-allyl
guanidines and aryl or alkenyl halides provide substituted 5-membered cyclic
guanidines in good yield. This method allows access to a number of different
cyclic guanidine derivatives in only two steps from readily available allylic
amines.
B. P. Zavesky, N. R. Babij, J. A. Fritz, J. P. Wolfe, Org. Lett., 2013,
15, 5420-5423.
A silver-catalyzed hydroamination of tosyl-protected N-allylguanidines
provides substituted cyclic guanidines in high yields. The reactions can be used
for construction of quaternary stereocenters as well as both monocyclic and
bicyclic guanidine products.
Z. J. Garlets, M. Silvi, J. P. Wolfe, Org. Lett.,
2016, 18, 2331-2334.
An intramolecular transition-metal-free base-mediated hydroamination of
propargylamine with isothiocyanates enables an atom-economical, regioselective
synthesis of diversely substituted imidazole-2-thiones and spiro-cyclic
imidazolidine-2-thiones in good yields via intramolecular 5-exo-dig
cycloisomerization.
A. Ranjan, R. Yerande, P. B. Wakchaure, S. G Yerande, D. H. Dethe, Org. Lett.,
2014,
16, 5788-5791.
A simple, commercially available iridium catalyst allows the use of sulfoxonium
ylides as a carbene source for various intra- and intermolecular X-H bond
insertions, including a practical ring-expansion strategy for lactams. The
safety and stability of sulfoxonium ylides recommend them as preferable
surrogates to traditional diazo ketones and esters.
I. K. Mangion, I. K. Nwamba, M. Shevlin, M. A. Huffman, Org. Lett., 2009,
11, 3566-3569.
Formation of iminophosphoranes in a Staudinger reaction and condensation with
carbon disulfide followed by condensation with α-amino esters provides
N-3-substituted 2-thiohydantoins.
S. Gosling, C. El Amri, A. Tatibouët, Synthesis, 2014, 46,
1079-1084.
An oxidative cascade cyclization strategy enables an unprecedented
construction of thiazole-2-thiones from enaminones via a cascade of C(sp2)-H/C(sp2)-H
bond sulfurations and C(sp3)-H bond thiocarbonylation. This
transformation allows for the efficient synthesis of thiazole-2-thiones with
broad tolerance in moderate to excellent yields from simple enaminones with
elemental sulfur.
B. Zhan, D. Liu, Y. Sun, Y. Zhang, J. Feng, F. Yu, Org. Lett., 2021, 23,
3076-3082.
A molecular iodine-catalyzed oxidative cyclization of 2-aminopyridine/amidine
and isothiocyanate via N-S bond formation enables the synthesis of N-fused and
3,4-disubstituted 5-imino-1,2,4-thiadiazole derivatives at ambient temperature.
This transition-metal-free protocol provides a facile and highly efficient
regiospecific synthesis of various 1,2,4-thiadiazole derivatives with good to
excellent yields using inexpensive I2 as a catalyst.
N. Tumula, N. Jatangi, R. K. Palakodety, S. Balasubramanian, M. Nakka, J. Org. Chem.,
2017, 82, 5310-5316.
In situ derived acyclic and cyclic 1,2-diaza-1,3-dienes (DDs) undergo an
interceptive [4 + 1] annulation with diazo esters (DEs) in the presence of
inexpensive copper(II) chloride to yield mono-, bi-, and tricyclic
4,5-dihydropyrazole-5-carboxylic acid derivatives.
O. A. Attanasi, L. De Crescentini, G. Favi, F. Mantellini, S. Mantenuto, S.
Nicolini, J. Org. Chem., 2014,
79, 8311-8338.
A novel palladium-catalyzed oxidative, intramolecular cyclocarbonylation
provides an efficient and direct approach for the construction of valuable
1,3,4-oxadiazole-2(3H)-ones and their derivatives.
F. Ji, X. Li, W. Guo, W. Wu, H. Jiang, J. Org. Chem.,
2015,
80, 5713-5718.
An unprecedented intermolecular cyclizative capture of the cyanamide anion and
several nitrile oxides enables the synthesis of 1,2,4-oxadiazol-5(4H)-imines.
Treatment of the imine products with concd. HCl furnishes 1,2,4-oxadiazol-5(4H)-ones.
S. V. Bhat, D. Robinson, J. E. Moses, P. Sharma, Org. Lett., 2016, 18,
1100-1103.
[RuCl2(CO)3]2/dppp is a highly effective
catalyst system for the intramolecular oxidative amination of various
aminoalkenes in presence of K2CO3 and allyl acetate in
N-methylpiperidine to give the corresponding cyclic imines and
indoles in excellent yields.
T. Kondo, T. Okada, T.-A. Mitsudo, J. Am. Chem. Soc., 2002, 124,
186-187.
A copper-promoted 6-endo-trig cyclization of readily available
β,γ-unsaturated hydrazones enables an efficient synthesis of a series of
1,6-dihydropyridazines with good yields, high functional group tolerance, and
remarkable regioselectivity under mild conditions. Importantly, the
1,6-dihydropyridazines can be efficiently converted to biologically important
pyridazines in the presence of NaOH.
Y.-Q. Guo, M.-N. Zhao, Z.-H. Ren, Z.-H. Guan, Org. Lett.,
2018, 20, 3337-3340.
Cu(II)-catalyzed aerobic 6-endo-trig cyclizations provide 1,6-dihydropyridazines and pyridazines via the judicious choice of
reaction solvent. Whereas 1,6-dihydropyridazines were obtained in good yields
with MeCN as the reaction solvent, employment of AcOH directly afforded
pyridazines in good yields.
Z. Fan, Z. Pan, L. Huang, J. Cheng, J. Org. Chem., 2019, 84,
4236-4245.
A highly efficient ruthenium-catalyzed stereospecific N-demethylative
rearrangement of isoxazolidines gives synthetically useful N-H-1,3-oxazinanes.
1,3-Oxazinanes are useful building blocks, which can be converted to
N-H-1,3-aminoalcohols in a subsequent step.
C.-Z. Yao, Z.-F. Xiao, X.-S. Ning, J. Liu, X.-W. Zhang, Y.-B. Kang, Org. Lett.,
2014,
16, 5824-5826.
A palladium-catalyzed cyclization reaction for the modular synthesis of highly
substituted piperazines and related bis-nitrogen heterocycles couples two of the
carbons of a propargyl unit with various diamine components to provide products
in very good yields with high regio- and stereochemical control.
T. D. Montgomery, V. H. Rawal, Org. Lett., 2016, 18,
740-743.
The use of cheap and innocuous reagents, such as NaClO2, NaOCl,
and catalytic amounts of TEMPO enables an environmentally friendly C(sp3)-H
oxidation of piperazines and morpholines to 2,3-diketopiperazines and
3-morpholinones, respectively. In addition, by using a stoichiometric amount of
TEMPO, 2-alkoxyamino-3-morpholinones can be prepared from morpholine derivatives.
D. Chamorro-Arenas, U. Osorio-Nieto, L. Quintero, L. Hernández-García, F.
Sartillo-Piscil, J. Org. Chem., 2018, 83,
15333-15346.
A cyclization of N-alkenylamides catalyzed by iodoarenes under oxidative
conditions enables the preparation of five-, six-, and seven-membered rings with
a range of substitutions. Preliminary data from the use of chiral iodoarenes as
precatalysts show that enantiocontrol is feasible.
A. Alhalib, S. Kamouka, W. J. Moran, Org. Lett.,
2015,
17, 1453-1456.
Regioselective ring closing ene-yne metathesis provided an efficient access to
different substituted 1-benzazepine scaffolds. Five- and six-membered lactams
were efficiently prepared by ring-closing metathesis affording highly
functionalizable compounds.
E. Benedetti, M. Lomazzi, F. Tibiletti, J.-P. Goddard, L. Fensterbank, M.
Malacria, G. Palmisano, A. Penoni, Synthesis, 2012, 44,
3523-3533.
An N-heterocyclic carbene catalyzes a highly enantioselective [3 + 3] annulation
reaction of N-hydroxyphthalimide (NHPI) 3,3-disubstituted acrylates and
N-Ts ketimines, providing the desired chiral dihydropyridinone products bearing
an all carbon quaternary stereogenic center in good yields with excellent
enantioselectivities. The reaction demonstrates that NHPI acrylates are
excellent substrates in NHC-catalysis.
Z. Zhang, X. Zeng, D. Xie, D. Chen, L. Ding, A. Wang, L. Yang, G. Zhong, Org. Lett.,
2015,
17, 5052-5055.
A wide screening of substrates in ring-closing metathesis reactions reveals the
great efficiency of phosphabicyclononane (phoban)-containing ruthenium-based
pre-catalysts. Comparison of the catalytic activities with Grubbs'
first-generation pre-catalyst illustrates the key role of the Phoban ligand.
F. Boeda, H. Clavier, M. Jordaan, W. H. Meyer, S. P. Nolan, J. Org. Chem., 2008,
73, 259-263.
Aminocarbonyl Group Containing Hoveyda-Grubbs-Type Complexes: Synthesis and
Activity in Olefin Metathesis Transformations
D. Rix, F. Caijo, I. Laurent, F. Boeda, H. Clavier, S. P. Nolan, M. Mauduit, J. Org. Chem., 2008,
73, 4225-4228.
Δ3-Aryl/heteroaryl substituted heterocycles via sequential Pd-catalysed
termolecular cascade/ring closing metathesis (RCM)
H. A. Dondas, B. Clique, B. Cetinkaya, R. Grigg, C. Kilner, J. Morris, V.
Sridharan, Tetrahedron, 2005,
61, 10652-10666.
An efficient enantioselective hydrazination/cyclization cascade reaction of
α-substituted isocyanoacetates to azodicarboxylates is catalyzed by a squaramide
catalyst derived from Cinchona alkaloid. The reaction affords optically
active 1,2,4-triazolines in excellent yields and very good enantioselectivities
under mild conditions.
M-X. Zhao, H.-L. Bi, H. Zhou, H. Yang, M. Shi, J. Org. Chem., 2013,
78, 9377-9382.
Organic phosphine-catalyzed [4
+ 2] annulation of
ethyl 2-(substituted-methyl)-2,3-butadienoates as 1,4-dipole synthons with N-tosylimines
gave ethyl
2,6-cis-disubstituted-1-(4-tosyl)-1,2,5,6-tetrahydro-pyridine-3-carboxylates
in excellent yields with complete regioselectivity and high diastereoselectivity.
X.-F. Zhu, J. Lan, O. Kwon, J. Am. Chem. Soc., 2003, 125, 4716-4717.
Fully substituted 4-aminopyrrolones are easily accessed starting from imines,
ketones, or α-bromophenyl acetonitriles. Imines are reacted with KCN/NH4Cl,
whereas ketones are transformed to the desired α-amino nitriles using a modified
Strecker reaction. Reaction with a suitable acyl halide produces the
corresponding amides. Ttreatment of these amides with ethanolic KOH gives
4-amino-1H-pyrrol-2(5H)-one derivatives in good yields.
H. Zali-Boeini, M. Mobin, K. Hajibabaei, M. Ghani, J. Org. Chem., 2012,
77, 5808-5812.
Pentafluorophenyl anion and trifluoromethyl anion as leaving groups enable a new
synthesis of 1,2,4-oxadiazol-5-ones from amidoximes using pentafluorobenzoyl
chloride or trifluoroacetic anhydride (TFAA) as a double acylating agent.
T. Gerfaud, H.-L. Wei, L. Neuville, J. Zhu, Org. Lett., 2011,
13, 6172-6175.
Ring-closing olefin metathesis (RCM)/elimination and RCM/oxidation/deprotection
of nitrogen-containing dienes are the key processes of new synthetic routes to
substituted 3-hydroxypyridines. An application of RCM/oxidation/deprotection
allows the synthesis of 3-aminopyridine derivatives.
K. Yoshida, F. Kawagoe, K. Hayashi, S. Horiuchi, T. Imamoto, A. Yanagisawa, Org. Lett., 2009,
11, 515-518.
A rhodium-catalyzed cycloisomerization converts various acyclic enynes to
their cyclic diene isomers with endoselectivity. Two different catalyst
systems have been developed, which are effective in promoting the C-C
bond-forming cyclization of enynes to furnish carbo- and heterocycles in
good to excellent yield. The mechanism is discussed.
H. Kim, C. Lee, J. Am. Chem. Soc.,
2005, 127, 10180-10181.
Ring-opening of cyclic sulfamidates with propargylic sulfonamides yielded
substrates for a gold-catalyzed cyclization to yield tetrahydropyrazines.
Subsequent reduction or multicomponent reactions of the tetrahydropyrazines gave
various piperazine scaffolds, that have a certain value in the synthesis of
novel screening compounds with lead-like molecular properties.
T. James, I. Simpson, J. Grant, V. Sridharan, A. Nelson, Org. Lett., 2013,
15, 6094-6097.
A Brønsted acid accelerated oxidative radical annulation of sulfonyl
hydrazones with simple olefins provides six-membered
heterocycles. The method offers a rapid and efficient approach to tetrahydropyridazines
which are key structural motifs in pharmaceutically active compounds.
X. Zhong, J. Lv, S. Luo, Org. Lett.,
2016, 18, 3150-3153.
Pd-catalyzed asymmetric carboetherification of γ,δ-alkenyl oximes with (hetero)aryl
and alkenyl halides in the presence of (R)-DTBM-SegPhos(O) enables a straightforward synthesis of highly enantioenriched
5,6-dihydro-4H-1,2-oxazines. Alternatively, commercially available (R)-DTBM-SegPhos
can be oxidized in situ in the presence of water without erosion of
enantiocontrol.
N. Li, B. Sun, S. Liu, J. Zhao, Q. Zhang,
Org. Lett., 2020, 22, 190-193.
A mild and highly efficient AgOTf catalyzed [3,3] sigmatropic rearrangement/1,3-H
shift/6π aza-electrocyclization cascade reaction of N-propargylic
hydrazones provides arious polysubstituted 1,6-dihydropyridazines with high
selectivity.
Z.-C. Ding, L-C. Ju, Y. Yang, X.-M. An, Y.-B. Zhou, R.-H. Li, H.-T. Tang, C.-K.
Ding, Z.-P. Zhan, J. Org. Chem.,
2016,
81, 3936-3941.
The reaction of in situ formed acyl isocyanates with amidines
provides disubstituted 1,3,5-triazinones with a low production cost and a simple
workup procedure. Chlorination and a further coupling reaction with various
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