Reactive intermediates. Part XV. Thermolysis of 1-(3,4-dihydro-4-oxoquinazolin-3-yl)-2-vinylaziridines. A new vinylaziridine rearrangement

1-(3,4-Dihydro-4-oxoquinazolin-3-yl)-2-vinylaziridines (I) undergo two competing thermal rearrangements: one to give the corresponding pyrrolines (II), and the other, a new type of rearrangement, to give the hydrazones (III). At higher temperatures a fragmentation involving cleavage of the N–N bond competes. An analogous thermal fragmentation of trans-2,3-diphenyl-1-phthalimidoaziridine (X) gives 2,3-diphenylazirine (XI), which in turn rearranges to 2-phenylindole. Reaction mechanisms are discussed.