Photocyclisation of enamides. Part II. Photocyclisation of N-benzoyl enamines of 1-tetralone to benzo[c]phenanthridines

Abstract

Irradiation of methanolic solutions of the N-benzoyl enamines (Ia–d) of 1-tetralone with a low-pressure mercury lamp caused stereoselective cyclisation to give the trans-tetrahydrobenzo[c]phenanthridones (IIIa–d), two of which were converted into the corresponding cis-isomers (VIIa and b) by heating with selenium. Further conversion into the BCcis-hexahydrobenzo[c]phenanthridine (XI) represents a potential route to natural products.