Intramolecular N–H insertion of α-diazocarbonyls catalyzed by Cu(acac)2: An efficient route to derivatives of 3-oxoazetidines, 3-oxopyrrolidines and 3-oxopiperidines

Cu(acac)2 was found to be an efficient catalyst for the intramolecular N–H insertion by carbenoids. The competitive intramolecular C–H insertion by carbenoids is not a problem in the diazo decomposition reaction with Cu(acac)2 as catalyst. The reaction provided derivatives of 3-oxoazetidine, 3-oxopyrrolidine and 3-oxopiperidine in moderate to good yields.