A new chiral Brønsted acid derived from carboxylic acid and a chiral oxazaborolidinium ion (COBI), as an activator, is introduced. This acid was successfully applied as a catalyst for the highly enantioselective protonation/nucleophilicaddition of diazoesters with carboxylic acids.
Desymmetrizing Asymmetric Ring Expansion of Cyclohexanones with α-Diazoacetates Catalyzed by Chiral Aluminum Lewis Acid
作者:Takuya Hashimoto、Yuki Naganawa、Keiji Maruoka
DOI:10.1021/ja202070j
日期:2011.6.15
in a 2:1 ratio was found to promote novel catalytic asymmetric ring expansion of cyclohexanone with α-substituted α-diazoacetates to give seven-membered rings with an all-carbon quaternary center. Application of this strategy to 4-substituted cyclohexanones opened up a novel way for the catalytic desymmetrizing asymmetric construction of cycloheptanones bearing remote α,δ-chiral centers.
Catalytic Asymmetric Insertion of Diazoesters into Aryl-CHO Bonds: Highly Enantioselective Construction of Chiral All-Carbon Quaternary Centers
作者:Lizhu Gao、Byung Chul Kang、Do Hyun Ryu
DOI:10.1021/ja408196g
日期:2013.10.2
This paper describes a catalytic enantioselective route to synthesize functionalized all-carbonquaternary acyclic systems via a boron Lewis acid-promoted formal C-C insertion of diazoesters into aryl-CHO bonds. In the presence of chiral (S)-oxazaborolidinium cation 1d as a catalyst, the reaction proceeded in good yield (up to 83%) with good regioselectivity (up to 88:12) and excellent enantioselectivity
N-Heterocyclic Carbene Boryl Iodides Catalyze Insertion Reactions of N-Heterocyclic Carbene Boranes and Diazoesters
作者:Thomas H. Allen、Takuji Kawamoto、Sean Gardner、Steven J. Geib、Dennis P. Curran
DOI:10.1021/acs.orglett.7b01777
日期:2017.7.7
Boron–hydrogen bond insertion reactions of N-heterocycliccarbene (NHC) boranes and diazoesters can be catalyzed by NHC-boryl iodides and produce stable α-NHC-boryl esters. The conditions of the reaction resemble the previous rhodium-catalyzed transformations (only the catalyst is different); however, the mechanisms of the two reactions are probably very different. The new boryl iodide catalyzed method is adept
Hydrazones obtained from alpha-diazo esters were converted to pyrroles when heated with thionyl chloride in alcohol. Among hydrazones, those substituted with a benzene ring on the beta-carbon to the ester are likely to give pyrroles in good yields. (C) 2013 Elsevier Ltd. All rights reserved.