Photochemical diaziridine syntheses

Photoisomerization of azomethinimines to diaziridines was observed in several classes of compound. Diazepine (271) was converted, even by sunlight, to its diaziridine isomer (68JA4738). Further photoisomerizations were observed with azomethinimines (272) obtained from pyrazolidones (70JPR161), and with some pyridazinium betaines (273). 

Even iV-aryldiaziridines can be obtained. Compound (274) is formed on irradiation of its 1,3-dipolar isomer, which is in thermal equilibrium with its head-to-tail dimer (82TH50800). 

A novel principle of diaziridine synthesis was found in nitrogen extrusion from tetrazolines (275). Af-Aryldiaziridines (276) almost unaccessible by older procedures thus become available (74CL185). 

A photochemical preparation of fluorodiaziridine (278) involves addition of HN3 to the imine (277) followed by UV irradiation (65JOC1398). 

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A photochemical diaziridine synthesis, analogous to the photoisomerization of nitrones, was worked out at suitable azomethine imines. By the action of sunlight, 104 is isomerized to the unstable diaziridine 105 in nearly 80% yield. 

A further photochemical diaziridine synthesis starts from tetrazolines like 109, which on irradiation lose nitrogen. In particular, the almost unknown A-aryldiaziridines became accessible by this procedure. ... 

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