Enantioselective NHC-Catalyzed Redox [4 + 2]-Hetero-Diels–Alder Reactions Using α,β-Unsaturated Trichloromethyl Ketones as Amide Equivalents
摘要:
alpha,beta-Unsaturated trichloromethyl ketones are suitable a alpha,beta-unsaturated amide and ester equivalents in N-heterocyclic carbene (NHC)-catalyzed redox hetero-Diels Alder reactions with azolium enolates generated from alpha-aroyloxyaldehydes. The initially formed syn-dihydropyranone products can be isolated or can undergo ring-opening with benzylamine followed by aminolysis of the resulting CCl3 ketone to form a range of diamides with high diastereo- and enantioselectivity (up to >95:5 dr and >99% ee).
Highly enantioselective synthesis of α-trichloromethyldihydropyrans catalyzed by bifunctional organocatalysts
摘要:
The enantioselective Michael addition of alpha-cyanoketones to alpha,beta-unsaturated trichloromethyl ketones was firstly reported. With a phenylalanine-derived bifunctional piperazine/thiourea catalyst, a series of alpha-trichloromethyldihydropyrans were obtained with up to 95% ee and 99% yield. (C) 2011 Elsevier Ltd. All rights reserved.
Isothiourea-Catalyzed Enantioselective Functionalization of 2-Pyrrolyl Acetic Acid: Two-Step Synthesis of Stereodefined Dihydroindolizinones
作者:Shuyue Zhang、James E. Taylor、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1021/acs.orglett.8b02423
日期:2018.9.7
Catalytic enantioselective functionalization of 2-pyrrolyl acetic acid with trichloromethyl enones using isothiourea catalysis is reported, leading to a range of stereodefined diesters and diamides after nucleophilic ring opening with either methanol or benzylamine (30 examples, up to >95:5 dr and >99:1 er). Subsequent intramolecular Friedel–Craftsreaction allows access to dihydroindolizinones in high yields
Organocatalytic Michael addition–lactonisation of carboxylic acids using α,β-unsaturated trichloromethyl ketones as α,β-unsaturated ester equivalents
作者:Louis C. Morrill、Daniel G. Stark、James E. Taylor、Siobhan R. Smith、James A. Squires、Agathe C. A. D'Hollander、Carmen Simal、Peter Shapland、Timothy J. C. O'Riordan、Andrew D. Smith
DOI:10.1039/c4ob01788a
日期:——
Isothiourea HBTM-2.1 catalyses the Michael addition–lactonisation of 2-aryl and 2-alkenylacetic acids and α,β-unsaturated trichloromethyl ketones. Ring-opening of the resulting dihydropyranones and subsequent alcoholysis of the CCl3 ketone with an excess of methanol gives a range of diesters in high diastereo- and enantioselectivity (up to 95 : 5 dr and >99% ee). Sequential addition of two different