Copper (I1) 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 diazocatbonyl compounds in the presence of Cu (OTf'j2, although the use of BF3. Et20 provides higher yields of the insertion producta. In contrast, the@, y-unsaturated diazo ketone 6 undergoes intramolecular ...