Photochemistry of 2′-substituted 1,2,3,4-tetrahydronaphthalene-1-spiro-3′oxaziridines. Variable-temperature 1H nuclear magnetic resonance spectroscopy of 1-substituted 1,3,4,5-tetrahydro-2H-1-benzazepin-2-ones

Abstract

The lack of regioselectivity of photorearrangement of the title spiro-oxaziridines in which the N-substituent is syn to the aromatic ring suggests that the first formed N–O–bond-cleaved species has a significant lifetime allowing rotation (inversion) to compete with rearrangement. The energy barrier to ring inversion of the title tetrahydro-1-benzazepin-2-ones is significantly influenced by the steric interaction between the N-substitutent and the peri hydrogen atom.