Meta, para and meta, ortho double exo nucleophilic additions of trimethylsilylester enolates derived from saturated and unsaturated carboxylic acids to tricarbonylchromium complexes of aryl ethers: dearomatizing cyclization to lactones

Potassium enolates derived from saturated and unsaturated bis(trimethylsilyl) ketene acetals react with tricarbonylchromium complexes of anisole and diphenylether to give, in addition to α-arylcarboxylic acids, the mono adducts, lactones, arising from a double exo nucleophilic addition. The latter were not observed in the case of benzenetricarbonylchromium. The intermediate dienol ethers could be isolated and fully characterized by X-ray crystallography. The influence of the nature of the substituents on the ketene acetals, of the nature of the oxidant, and of the nature of the ester enolates on the course of the reaction has been established and will be discussed.