Asymmetric nitrogen. Part 75. Stereochemistry of diaziridinyl radicals

ESR spectra have been recorded for the 3,3-dimethyl-, 3,3-bis(trifluoromethyl)- and 3,3-bis(methoxycarbonyl)-2-alkyldiaziridinyls (6)-(10), as well as the bicyclic diaziridinyls (13)–(15), generated by the photolysis of 5-substituted exo-6-chloro-1,6-diazabicyclo[3.1.0]hexanes. Theoretical ab initio MO calculations (UHF 3-21 G) on the simplest diaziridinyl (5) have been performed. Diaziridinyl radicals in the ground state have a pyramidal configuration at the trico-ordinated nitrogen atom. The difference between the theoretically calculated inversion barriers of diaziridinyl (5) and diaziridine (11) is 67.2 kJ mol–1 and between the experimental inversion barriers of 2-isopropyl-3,3-bis(trifluoromethyl)diaziridinyl (7) and the corresponding NH-diaziridine is 78.7 kJ mol–1. The bicyclic diaziridinyls (13)–(15) prefer the boat conformation.