Matrix-IR Spectroscopic Investigations of the Thermolysis and Photolysis of Diazoamides
journal contributionposted on 01.11.2013, 00:00 by Curt Wentrup, Hervé Bibas, Arvid Kuhn, Ullrich Mitschke, Mark C. McMills
Matrix photolysis of N,N-dialkyldiazoacetamides 1a–d at 7–10 K results in either the formation of C–H insertion products (in case of N,N-dimethyl and N,N-diethyl diazoamides) or almost exclusive Wolff rearrangement to ketenes (in the case of the cyclic diazoamides N-(diazoacetyl)azetidine and N-(diazoacetyl)pyrrolidine). This can be ascribed to higher activation barriers for the approach of the singlet carbene p orbital in 5 (or of the diazo carbon in an excited state of 1) to the stronger and “tied back” nature of the C–H bonds in the cyclic substituents. In contrast, flash vacuum thermolysis (FVT) of diazoamides 1a–d, in which reactions of excited states are excluded, gives rise to clean C–H insertion with only minor Wolff rearrangement to ketenes.