Unusual photocyclisation of 1-(N-methyl-1-naphthoylamino)tetramethylcyclohexene; X-ray crystal structure of 4b,8,9,10,10a,10b,11,12-octahydro-6,8,8,10-tetramethyl-10,12-methanobenzo[i]-phenanthridin-5(6H)-one

Abstract

Irradiation of 1-(N-methyl-1-naphthoylamino)-3,3,5,5-tetramethylcyclohexene (1a) first afforded the photocyclised B/C-trans-benzo[i]phenanthridinone (2a) which then underwent photoisomerisation to the corresponding cis-isomer (3a) and unusual cyclisation to the cage compound (4), the structure of which was established by X-ray analysis.