Direct dichlorovinylation of some carbonyl compounds by trichloroethylene under conditions of phase-transfer catalysis

Reaction of ketones 1 and 3 with trichloroethylene (TRI) carried out in the presence of 50% aq. NaOH and TBAHS as a catalyst, in ethyl ether (phase-tr ansfer catalysis, PTC) afford 1,2-dichlorovinylated ketones 2 and 4, respec tively in good yields, usually as mixtures of Z and E isomers. PTC reaction of aldehydes 5 with TRI, carried out with DMSO instead of TBAHS, yields O- dichlorovinylated products 6, as mixtures of isomers in the case of 6a. The se products are formed via C- or O-addition of ambident enolate anions to d ichloroacetylene (generated from TRI by a base) and fast protonation of hig hly basic dichlorovinyl anions thus formed. (C) 2000 Elsevier Science Ltd. All rights reserved.