ChemInform Abstract: Synthesis of 1,4-Keto Esters and 1,4-Diketones via Palladium-Catalyzed Acylation of Siloxycyclopropanes. Synthetic and Mechanistic Studies.

Abstract

The reaction of a variety of siloxycyclopropanes with acid chlorides in the presence of a catalytic amount of a palladium/phosphine complex gives 1,4-dicarbonyl compounds to good yield. 1-Alkoxy-1-(trialkylsiloxy)-cyclopropanes react with both aromatic and aliphatic acid chlorides in chloroform to give 1,4-keto esters. Synthesis of 1,4-diketones by the acylation of 1-alkyl- or 1-aryl-1-siloxycyclopropanes has been achieved by carrying out the reaction if HMPA under 10−20 atm of carbon monoxide. Kinetics studies and product analysis revealed the unique mechanism of this reaction, which involves rate-determining cleavage of the strained cyclopropane carbon−carbon bond with a coordinatively unsaturated acylpalladium chloride complex. Ab initio calculations of hydroxylated cyclopropane model compounds showed that the unique reactivities of the siloxycyclopropanes may be correlated with the molecular orbital properties of these compounds rather than their ground-state structural properties