Potassium carbonate is a remarkable base in the Wittig reaction. It promotes the formation of ethylenic compounds in excellent yields, by a biphasic solid-liquid process. There is modest reactivity in the presence of hydroxides. The Z-isomer is the major product in aprotic media whereas the E-isomer is promoted in protic media. The addition of phase-transfer agents accelerates the reaction. However sodium hydroxide on alumina can be used as the basic system for the Wittig reaction.

Abstract

Various 3,4-dihydropyrimidinones can be prepared via Biginelli reaction in aqueous media by using quaternary ammonium salts of different alkyl groups (C4 and C8) and anions (Cl − and Br − ) as catalysts. The use of quaternary ammonium salts along with longer alkyl chains increases the yield of the Biginelli reaction; however, bromide ammonium salts are less active than the chloride ones.