POLYMERIC CINCHONA ALKALOIDS AS CATALYSTS IN THE ENANTIOSELECTIVE 2,2-CYCLOADDITION REACTION OF KETENE AND CHLORAL

Abstract

Poly(cinchona alkaloid-co-acrylonitrile) 1a-d and poly(cinchona alkaloid acrylate) 2a-b catalyze the enantioselective cycloaddition of ketene to chloral for the preparation of (R)- and (S)-beta-(trichloromethyl)-beta-propiolactone. Copolymers 1a-d showed relatively lower catalytic activity with moderate enatioselectivity (22-59% e.e.), while homopolymers 2a-b gave similar catalytic activity and enatioselectivity (60-94% e.e.) compared to those of their monomeric alkaloids as catalysts. The polymeric effect was observed with poly(acryloyl quinidine) 2a as catalyst to get the best enantioselectivity of 94% e.e. at the temperature -30 degrees C.