Monoallylation and benzylation of dicarbonyl compounds with alcohols catalysed by a cationic cobalt(iii) compound

Abstract

Monoallylation and monoalkylation of diketones and β-keto esters with allylic and benzylic alcohols catalysed by [Cp*Co(CH₃CN)₃][SbF₆]₂ (I) are reported. The method does not require any additive and affords regioselective products. The mechanistic investigations were done by in situ ¹H NMR spectroscopy as well as control experiments. It has been shown that reactions proceed via η³-allyl complex formation or ally ether intermediate. The alkylation takes place via only ether intermediate. The resulting allylated and alkylated products have been used for the synthesis of eleven new trisubstituted pyrazoles and one pyrazolone.