Synthesis of Polycyclic δ-Lactams with Bridged Benzomorphan Skeleton: Selectivity and Diversity Driven by Substituents.

An efficient synthesis of bromofunctionalized 2,6-methano- and 1,5-methano-benzomorphanones, starting from easily available 6-benzyl-3,6-dihydropyridin-2(1H)-ones, is described. Furthermore, the synthesis of bridged benzomorphanones with hitherto not known polycyclic systems containing 2- or 3-azabicyclo[4.1.0]heptane units is developed upon treatment of both 2,6- and 1,5-methanobromobenzomorphans with t-BuOK. The effects of substituents on the diversity and stereoselectivity of both transformations are studied.