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

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 alpha,beta-acetylenic ketones and alkylation of 1,3-dicarbonyl and -dicyano compounds. The Michael addition to alpha,beta-unsaturated ketones proceeds in the usual way, giving the monoaddition products, whereas addition to alpha,beta-unsaturated esters and nitrites leads exclusively to the bis-addition products. The a,p-acetylenic ketones undergo double conjugate addition with thiols producing beta-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. (c) 2006 Elsevier Ltd. All rights reserved.