Reaction of ketenes. Part 18. Catalysed reactions between α-diazocarbonyl compounds and ketene acetals

Abstract

In the presence of copper powder or Cu(acac)₂, ethyl diazoacetate reacts with dialkylketene acetals to give cyclopropanes (2) whilst with ketene acetals having at least one hydrogen atom at position 2 both cyclopropanes (2) and butenoates (3) are formed. Noteworthy in these reactions is the fact that the α-diazoester fails to give dihydrofurans (1), which are the only reaction products when α-diazoketones are the employed α-diazocarbonyl compounds. The results can be rationalized on the basis of the intermediacy of a species in which α-diazocarbonyl compound, catalyst, and ketene acetal are involved.