Oxidative thermal nitrene generation

Abramovitch, Challand, and Yamada322 added thermally DMAD to 2-azido-3,4,5,6-tetrachloropyridine (172) and obtained 85% of the 1,2,3-triazole derivative (173), with no evidence for the generation of the nitrene. A one-step furopyridine synthesis of a mixture of 175 and 176 is achieved by treating the 1-oxide 174 with DMAD in hot toluene, rearrangements having taken place.323... 

The nitrogen source for the aziridination of alkenes, a nitrene or nitrenoid, can be generated in various ways (1) oxidation of a primary amine (2) base-induced -elimination of HX from an amine or amide with an electronegative atom X (X = halogen, O) attached to the NH group or by -elimination of metal halides from metal A-arenesulfonyl-A-haloamides (3) metal-catalyzed reaction of [A-(alkane/arenesulfonyl)imino]aryliodanes (4) thermolytic or photolytic decomposition of organyl azides and (5) thermally induced cycloreversion reactions . 

Direct preparation of an aziridine from an alkene is possible by reaction of the alkene with a nitrene or metal nitrenoid species. Nitrenes can be generated thermally or photochemically from azides, although their reaction with alkenes to give aziridines is often low yielding and is complicated by side reactions. Oxidation of iV-amino-phthalimide or related hydrazine compounds (e.g. with Pb(OAc>4 or by electrolysis) and reaction with an alkene has found some generality. The metal-catalysed reaction of nitrenes with alkenes has received considerable study. A variety of metal catalysts can be used, with copper(II) salts being the most popular. For example, styrene was converted to its A-tosyl aziridine 72 by reaction with [A-(tosyl)imino]phenyliodinane (PhI=NTs) and copper(II) triflate (5.75). ... 

Photochemical reactions of nitroso oxides at low temperatures with stilbenes have been reported [35]. Several singlet nitroso oxides were generated by the thermal reaction of triplet nitrenes with triplet oxygen at 95 K in 2-methyltetrahydrofuran. After photolysis of the nitroso oxides at 77 K, the formation of intermediates was observed. From spectroscopic and kinetics data, the authors postulated the formation... 

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