Catalytic Decomposition of Ethyl Diazopyruvate in the Presence of Electron-Deficient and Hydrocarbon Alkenes. Cyclopropanation vs. Carbon-Hydrogen Insertion

Article abstract of DOI:10.1021/jo01314a015

The bis(copper acetylacetonate)-catalyzed decomposition of ethyl diazopyruvate (EDP, 1) in the presence of electron deficient and hydrocarbon alkenes has been examined.The steric and electronic factors governing the reaction were evaluated.While mono- and disubstituted hydrocarbon alkenes such as cyclohexene, 4-(tert-butylmethylene)cyclohexane, styrene, and indene furnished the corresponding ethoxalylcyclopropane derivatives in moderate to satisfactory yields, polysubstituted alkenes such as 1-methylcyclohexene and 1,2-dimethylcyclohexene did not give separable adducts.Electron-withdrawing substituents (Cl, Br, NO2) directly bond to the substrate olefin and substitution of two phenyl groups in conjugation with the alkene precluded the formation of adducts.Only α-chloro- and p-chlorostyrene were found reactive toward the EDP-derived copper carbenoid.No C-H insertion products were detected in any case.It is shown that products of apparent allylic C-H insertion are actually the consequence of a 1,5 hydrogen shift of the initially formed cyclopropane.The evidence collected suggests that the EDP copper carbenoid is slightly less electrophilic than the copper carbenoid derived from ethyl diazoacetate.