Reactions of polyfluorinated cyclohexadienones with diazoalkanes. Part 1. Formation of cyclopropanes from polyfluorinated cyclohexa-2,4-dienones with diazomethane and phenyldiazomethane

Abstract

The reaction of 6-chloro-2,3,4,5,6-pentafluorocyclohexa-2,4-dienone (1) with diazomethane gives a mixture of two diastereoisomers of 6-chloro-3a,4,5,6,7a-pentafluoro-3,3a,6,7a-tetrahydrospiro[indazole-7,2′-oxirane] 2a and 2b. In contrast phenyldiazomethane reacts with polyfluorinated cyclohexa-2,4-dienones 1, 9, and 10 in acetonitrile to form the fluorinated 7-phenylbicyclo[4.1.0]hept-4-en-2-ones 4a,b, 11a,b and 12a,b as the main products. This reaction shows a remarkable dependence on the polarity of the solvent. While a complex mixture of products was formed in pentane, the reaction in acetonitrile proceeds with high stereoselectivity giving only the two endo-isomers.