Photocyclisation of enamides. Part 23. Reductive photocyclisation of enamides

Abstract

Irradiation of the enamides (1), (9), and (13) in the presence of sodium borohydride led to reductive photocyclisation to afford two types of hydrogenated lactams, the lactams with a conjugated diene moiety (4a–c), (5), (10a and b), and (11) and the lactams with an unconjugated diene moiety (6a–c), (12a and b), and (14) respectively, whose ratios were dependent on the solvent used. Deuterium-incorporation experiments provided important information on the mechanism of this reductive photocyclisation.