Reactions of ortho-substituted α,α-dibromoacetophenones with nucleophiles: first examples of combined carbophilic and bromophilic attack on C–Br bonds
摘要:
An efficient method for the formation of alpha-carbonyl-monosubstituted acetophenones from ortho-methoxy-and ortho-hydroxy-alpha,alpha-dibromoacetopheiiones and a range of selected nucleophiles, occurring via a carbophilic substitution/bromophilic substitution/protonation cascade process, is described. In turn, the preparation of alpha,alpha-dibromoacetophenones, isolated in high yields, relies on the neighboring group participation of the ortho-substituents in the starting ortho-substituted acetophenones. (C) 2008 Elsevier Ltd. All rights reserved
Here, we report the organocatalytic enantioselective synthesis of dihydrothiopyran derivatives from trans racemic donor-acceptor cyclopropane carbaldehydes (DACCs) and 2-mercapto-1-arylethanone via formal thio (4+2) cycloaddition involving thia-Michael aldol condensation and annulation. Mechanistic studies indicate a typical kinetic resolution (KR) is involved in this transformation, which results