Categories: C-C Bond Formation > Chains >
Benzylic Substitutions, Benzylation
| Related: |
 |
 |
 |
Recent Literature
Cs2CO3 promotes a general transition-metal-free
cross-coupling between benzylic sulfonylhydrazones and alkyl
boronic acids. The reaction is operationally simple and exhibits a broad
substrate scope.
R. R. Merchant, J. A. Lopez,
Org. Lett., 2020, 22, 2271-2275.
A metal-free carbon-carbon bond-forming coupling between tosylhydrazones and
boronic acids is very general and functional-group tolerant. As the required
tosylhydrazones are easily generated from carbonyl compounds, it can be seen as
a reductive coupling of carbonyls, a process of high synthetic relevance that
requires several steps using other methodologies.
J. Barluenga, M. Tomás-Gamasa, F. Aznar, C. Valdés, Nat. Chem., 2009,
1, 494-499.
The reaction of secondary and tertiary alkyl halides with benzylic or allylic
Grignard reagents in the presence of a catalytic amount of silver nitrate in
ether yielded the corresponding cross-coupling products in high yields. The
coupling reaction provides efficient access to quaternary carbon centers.
H. Someya, H. Ohmiya, H. Yorimitsu, K. Oshima, Org. Lett., 2008,
10, 969-971.
Activation of tertiary benzylic alcohols with SOCl2 or concentrated
HCl followed by treatment with trimethylaluminum allows the synthesis of m-tert-alkylbenzenes
in good yields. This reaction sequence is successful in the presence of a
variety of functional groups, including acid-sensitive and Lewis-basic groups.
In addition to t-Bu groups, 1,1-dimethylpropyl and 1-ethyl-1-methylpropyl
groups can also be installed.
J. A. Hartsel, D. T. Craft, Q.-H. Chen, M. Ma, P. R. Carlier, J. Org. Chem., 2012,
77, 3127-3133.
Sarcosine is an excellent ligand for cobalt-catalyzed carbon-carbon
cross-coupling of Grignard reagents with allylic and vinylic bromides. The
system performs efficiently when phenyl and benzyl Grignards are coupled with
alkenyl bromides. Notably, previously unachievable Co-catalyzed coupling of
allylic bromides with Grignards to linearly coupled α-products was also realized.
R. Frlan, M. Sova, S. Gobec, G. Stavber, Z. Časar, J. Org. Chem.,
2015,
80, 7803-7809.
The use of the Xantphos ligand in a mild palladium-catalyzed Kumada-Corriu
reaction of secondary benzylic bromides with aryl and alkenyl Grignard reagents
minimizes the undesired β-elimination pathway. The corresponding cross-coupling
products can be isolated in good yields with inversion of the configuration.
A. López-Pérez, J. Adrio, J. C. Carretero, Org. Lett., 2009,
11, 5514-5517.
The reaction of benzylic trichloroacetimidates with trimethylaluminum under
Lewis acid promoted conditions provides the corresponding methylated products.
Most benzylic trichloroacetimidates undergo ready displacement, with electron
deficient systems being the exception. The use of an enantiopure imidate showed
significant racemization, implicating the formation of a cationic intermediate.
N. S. Mahajani, J. D. Chisholm, J. Org. Chem., 2018, 83,
4131-4139.
Bu4NI as additive accelerates the palladium(0)-catalyzed
cross-coupling between benzylic zinc bromides and aryl or alkenyl triflates.
Remarkably, it further enables a new nickel(0)-catalyzed cross-coupling between
functionalized benzylic zinc reagents and primary alkyl iodides under mild reaction conditions.
M. Piber, A. E. Jensen, M. Rottländer, P. Knochel,
Org. Lett., 1999, 1, 1323-1326.
An insoluble, amphiphilic and polymeric palladium catalyst (PdAS) is an excellent catalyst for the
Suzuki-Miyaura reaction. The catalyst is reusable after easy work up and showed
good stability in any reaction medium.
Y. M. A. Yamada, K. Takeda, H. Takashashi, S. Ikegami, J. Org. Chem.,
2003,
68, 7733-7741.
An efficient α-deprotonation and functionalization of benzylboronates with
a wide range of electrophiles offers
high atomic efficiency and an alternative C-C bond disconnection for the
synthesis of benzylboronates. Notably, the boryl
group enables high diastereoselectivities when unsymmetrical secondary
α-bromoesters are used.
H. Jin, J. Han, X. Liu, C. Feng, M. Zhan, Org. Lett., 2023, 25,
4168-4172.
An enantioselective nickel-catalyzed Negishi cross-coupling of racemic secondary
benzylic bromides and chlorides is described. The catalyst components are
commercially available and air-stable, and the reaction is not highly oxygen- or
moisture-sensitive.
F. O. Arp, G. C. Fu, J. Am. Chem. Soc.,
2005,
127, 10482-10483.
Alkenyltrifluoroborates can be cross-coupled
with allyl and benzyl chlorides using KOH as base in acetone-water (3:2) at 50
°C and low catalyst loadings of a 4-hydroxyacetophenone oxime derived
palladacycle giving the corresponding 1,4-dienes and allylarenes, respectively.
The use of overheated water as solvent and K2CO3 as base
allows a coupling of alkenyltrifluoroborates with aryl and heteroaryl
bromides.
E. Alacid, C. Nájera, J. Org. Chem., 2009,
74, 2321-2327.
B(C6F5)3 catalyzes a highly effective
allylation of secondary benzylic alcohol derivatives with allylsilanes. The
reaction tolerates a broad range of additional functionalities, such as bromo,
acetoxy, and primary benzyloxy groups.
M. Rubin, V. Gevorgyan,
Org. Lett., 2001, 3, 2705-2707.
A Ni-catalyzed asymmetric reductive cross-coupling between vinyl bromides and
benzyl chlorides provides direct access to enantioenriched products bearing
aryl-substituted tertiary allylic stereogenic centers from simple, stable
starting materials. A broad substrate scope can be converted under mild reaction
conditions without pregeneration of organometallic reagents and the
regioselectivity issues commonly associated with allylic arylation.
A. H. Cherney, S. E. Reisman,
J. Am. Chem. Soc., 2014,
136, 14365-14366.
An Ir-catalyzed enantioselective benzylation reaction of allylic
electrophiles can occur directly from aryl acetic acids via stereoselective
carbon-carbon bond formation followed by decarboxylation as the terminal event.
The absence of a highly basic nucleophile offers broad functional group
compatibility that would not be possible employing established protocols.
P. J. Moon, Z. Wei, R. J. Lundgren, J. Am. Chem. Soc.,
2018,
140, 17418-17422.
The air-stable nickel(II) complex trans-(PCy2Ph)2Ni(o-tolyl)Cl
enables an internally selective Mizoroki-Heck-type coupling of substituted
benzyl chlorides with terminal alkenes at room temperature. This operationally
simple and highly regioselective reaction provides rapid, convergent access to
substituted allylbenzene derivatives in high yield and can be carried out on the
benchtop with no purification or degassing of solvents or reagents.
E. A. Standley, T. F. Jamison, J. Am. Chem. Soc., 2013,
135, 1585-1592.
Nickel-catalyzed intermolecular benzylation and heterobenzylation of unactivated
alkenes with benzyl chlorides provides functionalized allylbenzene derivatives.
In contrast to analogous palladium-catalyzed processes, all reactions described
herein employ electronically unbiased aliphatic olefins (including ethylene),
proceed at room temperature, and provide 1,1-disubstituted olefins with very
high selectivity.
R. Matsubara, A. C. Gutierrez, T. F. Jamison, J. Am. Chem. Soc., 2011,
133, 19020-19023.
Electrochemistry enables smooth Zn-mediated allylic alkylations in aqueous media
under air in the presence of a Pd catalyst between a full range of alkyl halides
(primary, secondary, and tertiary) and substituted allylic halides.
Y.-L. Lai, J.-M. Huang, Org. Lett.,
2017, 19, 2022-2025.
A photoinduced, copper-catalyzed, three-component reaction of haloalkane,
alkenes, and alkyne under mild reaction conditions helps to introduce privileged
functionalities into propargylic systems.
Y. Zhang, D. Zhang, J. Org. Chem., 2020, 85,
3213-3223.
The combination of a halogen bond donor with trimethylsilyl halide is an
efficient cocatalytic system for a direct dehydroxylative coupling reaction of
alcohol with various nucleophiles, such as allyltrimethylsilane and
trimethylcyanide, to give the corresponding adduct in moderate to excellent
yields.
M. Saito, N. Tsuji, Y. Kobayashi, Y. Takemoto, Org. Lett.,
2015,
17, 3000-3003.
A room temperature Pd-catalyzed allylic substitution of a wide range of soft
nucleophiles derived from diarylmethane provides rapid access to the
corresponding allylated products. A procedure for Pd-catalyzed allylic
substitutions to afford diallylation products with quaternary centers is also
described.
S.-C. Sha, J. Zhang, P. J. Carroll, P. J. Walsh, J. Am. Chem. Soc.,
2013,
135, 17602-17609.
An sp3 C-H bond-transformation reaction of methylarenes provides the
corresponding allylbenzene derivatives in good yields in the presence of
tetrabutylammonium iodide and tert-butyl hydroperoxide at 80 °C.
F. Shahsavari, A. Abbasi, M. Ghaznafarpour-Darjjani, S. M. Ghafelebashi, M.
Daftari-Besheli,
Synlett, 2017, 28, 1646-1648.
The Suzuki-Miyaura cross-coupling reaction between a diborylmethane derivative
and allyl halides or benzyl halides proceeded efficiently in the presence of an
appropriate Pd-catalyst at room temperature. The present approach provides
functionalized homoallylboronates and alkylboronates with excellent regio- and
chemoselectivities.
K. Endo, T. Ohkubo, T. Ishioka, T. Shibata, J. Org. Chem., 2012,
77, 4826-4831.
CsF with 1.1 equiv of H2O effects highly efficient
protodeboronation on tertiary diarylalkyl boronic esters with essentially
complete retention of configuration, whereas TBAFˇ3H2O can be used
for tertiary aryldialkyl boronic esters. Furthermore, substituting D2O
for H2O provides ready access to deuterium-labeled enantioenriched
tertiary alkanes. A short synthesis of the sesquiterpene (S)-turmerone is
described.
S. Nave, R. P. Sonawane, T. G. Elford, V. K. Aggarwal, J. Am. Chem. Soc., 2010,
132, 17096-17098.
Various acetals or alcohols react with allyl(trimethyl)silane or
1-phenyl-2-(trimethylsilyl)acetylene in the presence of a catalytic amount of
the Brřnsted acid o-benzenedisulfonimide under mild conditions to give
good yields of the allylated products. The catalyst can be easily recovered and
purified for use in further reactions.
M. Barbero, S. Bazzi, S. Cadamuro, S. Dughera, C. Piccinini, Synthesis, 2010,
315-319.
An enhanced Lewis acid system of InCl3 and Me3SiBr can be used to promote a
wide range of direct coupling reactions between alcohols and silyl nucleophiles
in non-halogenated solvents. Highly chemoselective allylations toward a hydroxyl
moiety over ketone and acetoxy ones have been demonstrated.
T. Saito, Y. Nishimoto, M. Yasuda, A. Baba, J. Org. Chem., 2006,
71, 8516-8522.
The reaction of alkoxides with boron trichloride results in the generation
of cations that can be allylated in subsequent transformations. The absence
of Brřnsted acids can make a significant difference in such syntheses.
G. W. Kabalka, M.-L. Yao, S. Borella, J. Am. Chem. Soc., 2006,
128, 11320-11321.
Aryl aldehydes couple readily with allylmetals to afford haloallylated products
in the presence of boron trihalides. The reactions tolerate a variety of
functional groups. Simple aqueous workup of haloallylation reactions, followed
by treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene, provides a straightforward
route to synthetically useful (E)-1,3-dienes.
M. P. Quinn, M.-L. Yao, G. W. Kabalka, Synthesis, 2011,
3815-3820.
An efficient Fe(III)-catalyzed direct coupling of alkenes with alcohols and
cross-coupling of alcohols with alcohols gives the corresponding substituted (E)-alkenes
stereospecifically. Mild conditions, atom efficiency, environmental soundness,
and stereospecificity are features that make this procedure very attractive.
Additionally, this reaction could be scaled up.
Z.-Q. Liu, Y. Zhang, L. Zhao, Z. Li, J. Wang, H. Li, L.-M. Wu, Org. Lett., 2011,
13, 2208-2211.
C-O bond cleavage of lithium alkoxides occurs readily at room temperature in the
presence of titanium(IV) halides. Capture of the resultant carbocation by
alkynes provides an efficient route to trisubstituted (E)-alkenyl halides
with high stereoselectivity.
M.-L. Yao, T. R. Quick, Z. Wu, M. P. Quinn, G. W. Kabalka, Org. Lett., 2009,
11, 2647-2649.
An efficient protocol for the palladium-catalyzed Heck alkynylation using XPhos
as ligand and Cs2CO3 as the base, couples a wide range of
functionalized terminal alkynes and substituted benzyl chlorides. An excess
amount of base and higher reaction temperatures allows the synthesis of allenes
in a one-pot procedure.
C. H. Larsen, K. W. Anderson, R. E. Tundel, S. L. Buchwald, Synlett, 2006,
2941-2946.
In the presence of Pd(OAc)2 and Xphos, alkynyl carboxylic acids
smoothly underwent a decarboxylative coupling reaction with various benzyl
halides or aryl halides, providing internal alkynes in good yields. It is
noteworthy that the optimal conditions are compatible with a wide range of aryl
halides.
W.-W. Zhang, X.-G. Zhang, J.-H. Li, J. Org. Chem., 2010,
75, 5259-5264.
A highly efficient palladium-catalyzed Sonogashira coupling of benzylic
ammonium salts with terminal alkynes provides a series of internal alkyne
derivatives in good yields. The reaction offers a broad substrate scope and high
functional group tolerance.
S. Xu, Z. Zhang, C. Han, W. Hu, T. Xiao, Y. Yuan, J. Zhao, J. Org. Chem., 2019, 84,
12157-12164.
The reaction of alkynylboron dihalides with benzylic, allylic, and
propargylic alcohols provides an efficient route to internal acetylenes
without isomerization of the product alkynes under the reaction conditions.
G. W. Kabalka, M.-L. Yao, S. Borella, Org. Lett.,
2006,
8, 879-881.
An enantioselective Cu-catalyzed borylative cross-coupling reaction of alkenes,
bis(pinacolato)diboron, and methyl iodide provides the desired methylboration
products with excellent diastereoselectivities and enantioselectivities.
B. Chen, P. Cao, Y. Liao, M. Wang, J. Liao, Org. Lett.,
2018, 20, 1346-1349.
A simple Cu(I) catalyst, generated in situ, is highly effective for
C-benzylation of nitroalkanes using abundant benzyl bromides and related
heteroaromatic compounds. This process proceeds via a thermal redox mechanism
and allows access to a variety of complex nitroalkanes under mild reaction
conditions.
P. G. Gildner, A. A. S. Gietter, D. Cui, D. A. Watson, J. Am. Chem. Soc., 2012,
134, 9942-9945.
Aryldiazomethanes can be generated in situ by simply heating the
tosylhydrazones of aromatic aldehydes in the presence of a stoichiometric amount
of base in polar protic solvents. In the presence of aldehydes, benzylic ketones
are formed in good yields. In addition, tosylhydrazones can be prepared in ethanol and
carried through the sequence without isolation.
S. R. Angle, M. L. Neitzel, J. Org. Chem., 2000,
65, 6458-6461.
A dual Ni/photoredox system was successfully employed to generate acyl
radicals from aldehydes via selective formyl C-H activation. A subsequently
cross-coupling with benzylic and allylic pyridinium salts provides ketones. The
reaction tolerates a broad range of functional groups.
V. Murugesan, A. Ganguly, A. Karthika, R. Rasappan, Org. Lett., 2021, 23,
5389-5393.
Benzylic Aroylation of Toluenes Mediated by a LiN(SiMe3)2/Cs+
System
Y. Gu, Z. Zhang, Y.-E. Wang, Z. Dai, Y. Yuan, D. Xiong, J. Li, P. J. Walsh,
J. Mao, J. Org. Chem., 2022, 87,
406-418.
A direct asymmetric copper hydride (CuH)-catalyzed coupling of α,β-unsaturated
carboxylic acids with aryl alkenes provides chiral α-aryl dialkyl ketones. The
reaction tolerates various substrate substitution patterns, sensitive functional
groups, and heterocycles.
Y. Zhou, J. S. Bandar, S. L. Buchwald, J. Am. Chem. Soc., 2017,
139, 8126-8129.
Cyclopentanone as an electron pair donor proved highly efficient for the
stabilization of allyl and vinyl cations in combination with a calcium-based
catalyst system. The system enabled a transition-metal-free intermolecular
carbohydroxylation of alkynes with allyl and propargyl alcohols.
T. Stopka, M. Niggemann, Org. Lett.,
2015,
17, 1437-1440.
An enantioselective Ni-catalyzed reductive cross-coupling of acid chlorides
with racemic secondary benzyl chlorides in the presence of Mn0 as a stoichiometric reductant generates acyclic α,α-disubstituted ketones in good
yields and high enantioselectivity. The mild, base-free reaction conditions
tolerate various functional groups on both coupling partners.
A. H. Cherney, N. T. Kadunce, S. E. Reisman, J. Am. Chem. Soc., 2013,
135, 7442-7445.
When used with photocatalysis, bench-stable, commercially available
collidinium salts are excellent radical precursors with a broad scope, that can
substitute alkyl halides. Furthermore, all of the reaction components are
water-soluble, which facilitates product isolation.
M. D. Rathnayake, J. D. Weaver III, Org. Lett., 2021, 23,
2036-2041.
The simple and inexpensive combination of
TiCl4(2,4,6-collidine) and manganese powder afforded a
low-valent titanium reagent, which facilitated homolytic cleavage of benzylic
C-OH bonds. Radical conjugate addition reactions of various benzyl alcohol
derivatives with electron-deficient alkenes furnished the corresponding
adducts in good yields.
T. Suga, S. Shimazu, Y. Ukaji, Org. Lett.,
2018, 20, 5389-5392.
An enantioselective Ni-catalyzed cross-coupling of N-hydroxyphthalimide
esters with vinyl bromides proceeds under mild conditions and uses tetrakis(N,N-dimethylamino)ethylene
as a terminal organic reductant. Good functional group tolerance is demonstrated,
with over 20 examples of reactions that proceed with excellent
enantioselectivity.
N. Suzuki, J. L. Hofstra, K. E. Poremba, S. E. Reisman, Org. Lett.,
2017, 19, 2150-2153.
A highly regio- and enantioselective copper-catalyzed reductive
hydroxymethylation of styrenes and 1,3-dienes with 1 atm of CO2
readily provides important chiral homobenzylic alcohols. Moreover, various
1,3-dienes were converted to chiral homoallylic alcohols with high yields and
excellent regio-, enantio-, and Z/E-selectivities.
Y.-Y. Gui, N. Hu, X.-W. Chen, L-L. Liao, J.-H. Ye, Z. Zhang, J. Li, D.-G. Yu, J. Am. Chem. Soc., 2017,
139, 17011-17014.
Very low loadings of iridium(I) complexes having an imidazol-2-ylidene ligand
with benzylic wingtips efficiently catalyze the β-alkylation of secondary
alcohols with primary alcohols and acceptorless dehydrogenative formation of
quinolines from 2-aminobenzyl alcohol and ketones through a borrowing hydrogen
pathway to provide the desired products in good yields.
S. Genç, B. Arslan, S. Gülcemal, S. Günnaz, B. Çetinkaya, D. Gülcemal, J. Org. Chem., 2019, 84,
6286-6297.
RuCl2(PPh3)3 as a precatalyst enables a simple
cross dehydrogenative coupling between two different primary alcohols via a
borrowing-hydrogen approach. The present methodology is applicable to a large
variety of alcohols including long chain aliphatic alcohols and heteroaryl
alcohols.
S. Manojveer, S. Salahi, O. F. Wendt, M. T. Johnson, J. Org. Chem., 2018, 83,
10864-10870.
Iron complexes are cheap and effective catalysts for a series of "umpolung"
nucleophilic additions of hydrazones at room temperature. The catalytic system
offers chemoselectivity and a broad substrate scope.
C.-C. Li, X.-J. Dai, H. Wang, D. Zhu, J. Gao, C.-J. Li, Org. Lett.,
2018, 20, 3801-3805.
A palladium-catalyzed C(sp3)-C(sp3) coupling
between benzyl chlorides and air-/moisture-stable N,N-dialkylaminomethyltrifluoroborate
salts provides substituted arylethylamines in good yields.
R. A. Lippa, D. J. Battersby, J. A. Murphy, T. N. Barrett, J. Org. Chem., 2021, 86,
3583-3604.
Boron Lewis acid promoted formal insertion of aryldiazoalkane into the C-H bond
of both aromatic and aliphatic aldehydes enables a novel, catalytic
enantioselective route to α-tertiary aryl ketones. In the presence of a chiral (S)-oxazaborolidinium
ion catalyst, the reaction proceeded in good yields with excellent
enantioselectivities.
B. C. Kang, D. G. Nam, G.-S. Hwang, D.-H. Ryu, Org. Lett.,
2015,
17, 4810-4813.
An ionic cobalt-PNP complex enables an efficient α-alkylation of ketones with
primary alcohols. A broad range of ketone and alcohol substrates provides
alkylated ketones in good yields. The method was also successfully applied to a
greener synthesis of quinoline derivatives using 2-aminobenzyl alcohol as the
alkylating reagent.
G. Zhang, J. Wu, H. Zeng, S. Zhang, Z. Yin, S. Zheng, Org. Lett.,
2017, 19, 1080-1083.
A manganese-catalyzed C-alkylation of carboxylic acid derivatives with
alcohols operates via hydrogen autotransfer and ideally produces water as the
only side product. Importantly, aliphatic-, benzylic-, and
heterocyclic-containing alcohols can be used as alkylating reagents, eliminating
the need for mutagenic alkyl halides.
Y. K. Jang, T. Krückel, M. Rueping, O. El-Sepelgy, Org. Lett.,
2018, 20, 7779-7783.
The use of 4-benzyl Hantzsch esters enables the construction of molecules with
all-carbon quaternary centers by visible light-induced photoredox catalysis via
transfer alkylation. Reactions of 4-alkyl Hantzsch nitriles as tertiary radical
donors joined two contiguous all-carbon quaternary centers intermolecularly.
W. Chen, Z. Liu, J. Tian, J. Li, J. Ma, X. Cheng, G. Li, J. Am. Chem. Soc., 2016,
138, 12312-12315.
A Ni-catalyzed carboxylation of benzyl halides with CO2 proceeds
under mild conditions at room temperature under atmospheric pressure. The method
does not require well-defined and sensitive organometallic reagents and thus is
user-friendly and operationally simple.
T. León, A. Correa, R. Martin, J. Am. Chem. Soc., 2013,
135, 1221-1224.
A highly efficient electrochemical desulfonylative carboxylation protocol
takes advantage of CO2 as the abundant C1 building block for the
facile preparation of multifunctionalized carboxylic acids, including the
nonsteroidal anti-inflammatory drug ibuprofen, under mild reaction conditions.
J.-S. Zhong, Z.-X. Yang, C.-L. Ding, Y.-F. Huang, Y. Zhao, H. Yan, K.-Y. Ye, J. Org. Chem., 2021, 86,
16162-16170.
Visible-light photoredox catalysis realizes an external-reductant-free cross-electrophile
coupling of tetraalkyl ammonium salts with carbonyl compounds and CO2. The byproduct trimethylamine serves as
the electron donor. Moreover, this protocol exhibits mild reaction conditions,
broad substrate scope, good functional group tolerance, low catalyst loading,
and facile scalability.
L.-L. Liao, G.-M. Cao, J.-H. Ye, G.-Q. Sun, W.-J. Zhou, Y.-Y. Gui, S.-S. Yan,
G. Shen, D.-G. Yu, J. Am. Chem. Soc.,
2018,
140, 17338-17342.
A nickel-catalyzed reductive carboxylation of styrenes using CO2
proceeds under mild conditions using diethylzinc as the reductant. The catalyst
system is very robust and will fixate CO2 in good yield even if
exposed to only an equimolar amount introduced into the headspace above the
reaction.
C. M. Williams, J. B. Johnson, T. Rovis, J. Am. Chem. Soc., 2008,
130, 14936-14937.
A
Ni-catalyzed dehydrogenative cross-coupling reaction cascade between readily available
alcohols and olefins enables a direct synthesis of α-arylated ketones. This cost-effective
method provides monoarylated ketones in good yields
with exclusive selectivity without using any advanced synthetic intermediates.
P.-F. Yang, W. Shu,
Org. Lett., 2020, 22, 6203-6208.
Transition metal carbenes can directly be generated from readily available and
stable 1-sulfonyl-1,2,3-triazoles in the presence of chiral Rh(II) carboxylates
and can be used in a highly efficient enantioselective C-H insertion of azavinyl
carbenes into unactivated alkanes to access various β-chiral sulfonamides.
S. Chuprakov, J. A. Malik, M. Zibinsky, V. V. Fokin, J. Am. Chem. Soc., 2011,
133, 10352-10355.
A bis(diisopropylamino)cyclopropenimine-substituted bis-protonated proton sponge
can be used as a bifunctional phase-transfer catalyst. The catalyst operates
simultaneously as a hydrogen bond donor and a phase-transfer catalyst,
facilitating the movement of charged intermediates from the interface to the
organic phase.
L. Belding, P. Stoyanov, T. Dudding, J. Org. Chem.,
2016,
81, 553-558.