Ionic liquid as catalyst and solvent: the remarkable effect of a basic ionic liquid, [bmIm]OH on Michael addition and alkylation of active methylene compounds

Abstract

A basic ionic liquid, 1-methyl-3-butylimidazolium hydroxide, [bmIm]OH, catalyzes the Michael addition of active methylene compounds to conjugated ketones, carboxylic esters and nitriles. It further catalyzes the addition of thiols to α ,β-acetylenic ketones and alkylation of 1,3-dicarbonyl and -dicyano compounds. The Michael addition to α ,β-unsaturated ketones proceeds in the usual way, giving the monoaddition products, whereas addition to α ,β-unsaturated esters and nitriles leads exclusively to the bis-addition products. The α ,β-acetylenic ketones undergo double conjugate addition with thiols producing β-keto 1,3-dithio-derivatives. In the alkylation reaction the acyclic 1,3-diketones are monoalkylated, whereas cyclic ketones undergo dialkylation under identical conditions. All these reactions were carried out without any organic solvent. The ionic liquid can also be recycled.