CYCLOADDITION OF DICLOROKETENE WITH FUNCTIONALIZED CYCLOALKENES. SYNTHESIS OF BICYCLOOCTANONE-3-YL DERIVATIVES AND OF 3,4-DICARBOXYMETHOXY-1-METHYLBICYCLOOCTAN-7-ONE

Article abstract of DOI:10.1016/S0040-4020(01)91870-8

Dichloroketene reacts with some cycloalkenes in wich an ester function is in homoallylic or in an even more remote position with respect to sp² carbon atoms.In fact acetate and benzoate of 3,5,5-trimethylcyclohex-3-en-1-ol and 1,2-dicarbomethoxy-4-methyl-cyclohex-4-ene undergo 2+2 cycloaddition of dichloroketene to produce the corresponding bicyclo<4.2.0>octanone derivatives in 60-65percent yield.In the latter case the process occurs regiospecifically to give 3,4-dicarboxymethoxy-1-methylbicyclo<4.2.0>octan-7-one as product after dechlorination.The Hassner zinc dehalogenation method of generating dichloroketene is the best procedure.