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).
The asymmetricepoxidation of electron‐deficient olefins has been achieved using inexpensive and readily available prolinols as catalysts with good to excellent yields and enantioselectivities. The utility of the resulting chiral epoxides was illustrated by elaboration to several synthetically useful compounds featuring a concise synthesis of (−)‐(5R,6S)‐balasubramide.
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
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
Enantioselective NHC-Catalyzed Redox [4 + 2]-Hetero-Diels–Alder Reactions Using α,β-Unsaturated Trichloromethyl Ketones as Amide Equivalents
作者:Nassilia Attaba、James E. Taylor、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1021/acs.joc.5b01820
日期:2015.10.2
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).