Regiochemical switching of Mitsunobu cyclisation mode of vicinal diamines with pendant hydroxyl group.

Ambident 1,2-diamines derived from the nitro-Mannich reaction containing both a tosyl amide and a secondary amine could be regioselectively cyclised through the tosyl amide onto a pendant primary hydroxyl group to give piperazine (60-75% yields) or 1,4-diazepane (71% yield) ring systems under Mitsunobu conditions. For some substrates addition of Et(3)N.HCl encouraged regioselective cyclisation through the secondary amine leading to aziridine ring systems.