N-Heterocyclic Carbene-Catalyzed Synthesis of α-Trifluoromethyl Esters
摘要:
The N-heterocyclic carbene (NHC)-catalyzed trifluoromethylation of alpha-chloro aldehydes was developed, allowing straightforward access to valuable alpha-trifluoromethyl ester derivatives. The unique combination of an electrophilic trifluoromethylation reagent with NHC catalysis was the key for the functionalization of a broad range of alpha-chloro aldehydes, and the products are formed in moderate to good yields. Investigations of the enantioselective version of this reaction afforded the enantioenriched products in moderate yields with good ee values.
Carbene and Acid Cooperative Catalytic Reactions of Aldehydes and <i>o</i>-Hydroxybenzhydryl Amines for Highly Enantioselective Access to Dihydrocoumarins
作者:Xingkuan Chen、Runjiang Song、Yingguo Liu、Chong Yih Ooi、Zhichao Jin、Tingshun Zhu、Hongling Wang、Lin Hao、Yonggui Robin Chi
DOI:10.1021/acs.orglett.7b02883
日期:2017.11.3
A highly enantioselective method for quick access to dihydrocoumarins is reported. The reaction involves a cooperative catalytic process with carbene and in situ generated Brønsted acid as the catalysts. α-Chloro aldehyde and readily available and stable o-hydroxybenzhydryl amine substrates were used to generate reactive azolium ester enolate and ortho-quinone methide (o-QM) intermediates, respectively
Chiral NHC-catalyzed 1,3-dipolar [3 + 2] cycloaddition of azomethine imines with α-chloroaldehydes for the synthesis of bicyclic pyrazolidinones
作者:Limin Yang、Yunbo Lv、Fei Wang、Guofu Zhong
DOI:10.1039/c8ob00925b
日期:——
A chiral N-heterocyclic carbene (NHC)-catalyzed 1,3-dipolar [3 + 2] cycloaddition reaction of 3-oxopyrazolidin-1-ium-2-ides and α-chloroaldehydes was developed for the synthesis of pyrazolo[1,2-a]pyrazole-1,7-diones in moderate to good yields (up to 76%) with good enantioselectivities (up to 98% ee) and diastereoselectivities (up to 8 : 1 dr).
A facile N-heterocyclic carbene catalytic enantioselective aza-Diels–Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study showed that cis-TSa, formed from a top face approach of oxodiazene to cis-IIa, is the most favorable transition state and is consistent with the experimental
Trifluoromethylthiolation of α-Chloroaldehydes: Access to Quaternary SCF<sub>3</sub>
-Containing Centers
作者:Fabien Gelat、Thomas Poisson、Akkattu T. Biju、Xavier Pannecoucke、Tatiana Besset
DOI:10.1002/ejoc.201800418
日期:2018.8.1
Munavalli reagent as the electrophilic SCF3 source, a base-catalyzed trifluoromethylthiolation reaction with a panel of -chloroaldehydes was successfully achieved under mild reaction conditions. The -trifluoromethylthiolated chloroaldehydes were obtained in moderate to high yields (up to 88%). This approach demonstrated a good functional-group tolerance and offered access to highly functionalized quaternary