The Synthetic Progress of Fused Bicyclic N,O-acetals

Owing to the prevalent occurring in natural products and abundant bioactivities, the effective synthetic methods of fused bicyclic N,O-acetals skeletons are of great interest to chemists. This mini-review summarized the thus far synthetic progress of fused bicyclic N,O-acetals. These works were elaborated according to the different reaction types, including a) hetero-Diels-Alder cycloaddition of cyclic enamines with oxadienes; b) step-by-step reactions between cyclic enamines and electrophiles with pendant hydroxyl groups; c) [3+2] cycloaddition of indole with quinone or its equivalent and d) other novel strategies. The catalytic systems and reaction mechanisms are mainly described.