Catalytic Role of Copper Triflate in Lewis Acid Promoted Reactions of Diazo Compounds

Article abstract of DOI:10.1021/jo00181a010

Copper(II)trifluoromethanesulfonate is often a superior catalyst for transformations of diazo compounds that are normally promoted by boron trifluoride etherate.Formal carbon-oxygen insertion occurs when ortho esters are reacted with diazocarbonyl compounds in the presence of Cu(OTf)2, although the use of BF3*Et2O provides higher yields of insertion products.In contrast, the β,γ-unsaturated diazo ketone 6 undergoes intramolecular cyclization to produce the corresponding cyclopentenone in higher yield with Cu(OTf)2 catalysis than with the use of BF3*Et2O.Intamolecular cyclopropanation of the γ,δ-unsaturated diazo ketone 8 occurs in exceptionally high yield in the presence of Cu(OTf)2, whereas with BF3*Et2O intramolecular cyclization occurs with extensive rearrangement anf fluoride transfer.Copper(II)triflate is unique among transition-metal catalysts that are normally employed for reactions with diazo compounds in its effectiveness for these transformations.