Development of 5-silylethynyl-1,3-dioxolan-4-one as a new prochiral template for asymmetric phase-transfer catalysis.

Phase-transfer catalyzed asymmetric alkylation and Michael addition of 5-silylalkynyl-1,3-dioxolan-4-one were developed as a novel strategy to provide highly modular tertiary α-alkyl-α-hydroxy acids bearing an alkyne moiety.

Phase-transfer-catalyzed asymmetric alkylation of alpha-benzoyloxy-beta-keto esters: stereoselective construction of congested 2,3-dihydroxycarboxylic acid esters.

Highly enantioselective phase-transfer-catalyzed alkylation of tert-butyl 2-benzoyloxy-3-oxobutanoate was realized by the use of an N-spiro chiral quaternary ammonium salt, as a complementary approach to the asymmetric hydroxylation of alpha-alkyl-beta-keto esters. The synthetic utility of the alkylated compounds is highlighted by the diastereoselective reduction and alkylation of the remaining ketone moiety to give various enantiomerically enriched congested 2,3-dihydroxycarboxylic acid esters.

Importance of chiral phase-transfer catalysts with dual functions in obtaining high enantioselectivity in the Michael reaction of malonates and chalcone derivatives.

[reaction: see text]. Highly enantioselective Michael addition of diethyl malonate to chalcone derivatives has been achieved under mild phase-transfer conditions by the successful utilization of N-spiro C(2)-symmetric chiral quaternary ammonium bromide 1 as a catalyst, which possesses diarylhydroxymethyl functionalities as a recognition site for the prochiral electrophile. This simple asymmetric Michael addition process was found to be quite effective for various chalcone derivatives, including those with heteroaromatic substituents.