Feeding sequence-regulated divergent (4 + 1 + 1′) annulations of α-bromo carbonyls and 1-azadienes via computational calculation-based mechanism elucidation

By investigating the mechanism of our previously reported (4 + 1 + 1) annulations of α-bromo carbonyls and 1-azadienes via density functional theory (DFT) calculations, the formation of a carbon anion intermediate and its attack on another α-bromo carbonyl substrate in a (4 + 1 + 1) manner were proposed as more reasonable processes. On this basis, a new controllable divergent (4 + 1 + 1′) reaction was realised by changing the feeding sequence of two different α-bromo substrates in the presence of tertiary amines and bases. A series of fused benzofuro[3,2-b]pyridines or benzo[4,5]thieno[3,2-b]pyridines with more functional diversity were efficiently constructed in moderate to excellent yields.