Reactions of diazirines leaving nitrogen in the molecule

Photolytic transformation of diazirines to diazoalkanes was observed in some cases. The parent compound (44) on irradiation in the gas phase with light (A = 3200 A) yields diazomethane. The quantum yield is 0.2 (64JA292). 

Formation of diazomethane from diazirine was also observed in a solid nitrogen matrix on irradiation (64JCP(41)3504). Labeling experiments demonstrated that elimination and uptake of nitrogen occurred. 

With some special diazirines interconversion with diazoalkanes was observed on illumination (79AHC(24)63), e.g. with diazirinecarboxylic acid piperidide (194), spirodiazirine (195) and the tetracyclic ketodiazirine (196) (78CC442). 

Thermal conversion of diazirines to linear diazo compounds was postulated occasionally and proved by indirect methods. The existence of a diazo compound isomeric to diazirine (197) was proved spectroscopically on short thermolysis in DMSO (76JA6416). An intermediate diazoalkane was trapped by reaction with acetic acid, yielding the ester (198) (77JCS(P2)1214). 

Methylvinyldiazirine (199) rearranges at room temperature in the course of some days. Formation of the linear isomer is followed by electrocyclic ring closure to give 3-methyl-pyrazole. The linear diazo compound could be trapped by its reaction with acids to form esters, while the starting diazirine (199) is inert towards acids (B-71MI50801). 

---