Ring-opening reactions of 7,7-dichlorobicyclo[3,2,0]hept-2-en-6-one and its conversion into methyl benzoate with methoxide ion

Abstract

The addition of methoxide and hydroxide ions, ammonia, and hydrazine to 7,7-dichlorobicyclo[3,2,0]hept-2-en-6-one (I) has led, by ring opening, to cis-dichloromethylcyclopentenecarboxylic acid derivatives (VI), which in the case of the methyl ester may epimerise to the trans-ester (VIIa). In polar aprotic solvents the ketone (I) gives rise to methyl benzoate, and deuterium labelling indicates that a bicyclo[3,1,0]hex-2-en-4-yl anion is involved.