Cu-Catalyzed Oxidative [3 + 2] Annulation of 2-(Pyridine-2-yl)acetates with Maleimides: Synthesis of 1 H -Pyrrolo[3,4- b ]indolizine-1,3-diones.

A novel protocol for the construction of highly functionalized indolizine derivatives, that is, 1 H -pyrrolo[3,4- b ]indolizine-1,3-diones (PIZDOs, 3 ) from 2-(pyridine-2-yl)acetates and maleimides via a regioselective oxidative [3 + 2] annulation was developed. The cascade oxidative reaction was enabled by heating a mixture of the two substrates in the presence of Ag 2 CO 3 as an oxidant and Cu(OAc)·H 2 O as a catalyst in chlorobenzene. Consequently, a series of PIZDOs 3 were synthesized with high regioselectivity in moderate yields. This protocol can be used in the synthesis of functionalized PIZDOs via the one-pot oxidative annulation reaction rather than through multistep reactions, which is suitable for both combinatorial and parallel syntheses of PIZDOs.