Partial asymmetric synthesis of 2-arylcyclopropane carboxylic acids by the reaction of sulphur ylides with β-arylacylates

Abstract

Condensation of (—)-emnthyl or (+)-bornyl β-arylacrylates (I) and dimethyloxosulphonium methylide or dimethylsulphonium methylide followed by alkaline hydrolysis gave optically active 2-arylcyclopropane carboxylic acids. Chemical yields of the cyclopropane derivatives decreased successively in the following order in the reaction of the cinnamates with: (a) trimethyloxosulphonium iodide in the presence of sodium hydride or potassium t-butoxide in dimethylsulphoxide solution, (b) trimethyloxosulphonium chloride, sodium hydride in tetrahydrofuran solution and (c) trimethylsulphonium iodide, sodium hydride in dimethylsulphoxide solution. Irrespective of the nature of the asymmetr-inducing centres and the method of condensation, cinnamates with or without ring-substituents gave, after hydrolysis, predominantly laevorotatory 2-arylcyclopropane carboxylic acids, while β-(α-naphthyl)acrylates afforded the dextrorotatory compounds in excess.