Cyclic guanidines. Part 2. Rearrangement of N-substituted 2-arylamino-4,5,6,7-tetrahydro-1H-1,3-diazepines. X-Ray molecular structure of 1-(2,6-dichlorophenyl)-2-(2-methylallylimino)hexahydro-1,3-diazepine

Abstract

1,3-Aryl migrations of title compounds (2) are shown to be triggered by base catalysis under mild conditions. Alternative rearrangement conditions, limiting factors, as well as the occurrence of byproducts, and competing products are investigated. A crossover experiment reveals the purely intramolecular nature of the Chapman-type rearrangement. The structure of the rearrangement product 1-(2,6-dichlorophenyl)-2-(2-methylallylimino)hexahydro-1,3-diazepine (3a) is confirmed by X-ray analysis. An explanation for the directionality of the reaction is furnished by an MNDO calculation on the reaction enthalpy.