Cu-catalyzed decarboxylative annulation of proline derivatives: multi-component synthesis of functionalized chromeno[2,3-c]-pyrrol-9(1H)-one derivatives

We developed a novel protocol for the preparation of functionalized chromeno[2,3-c]pyrrol-9(1H)-one derivatives (CMPOs) 3 and 3 ' from 3-formylchromones with proline derivatives. This strategy involved an unprecedented cascade reaction entailing simple heating of a mixture of substrates 1 with 2 and toluene, followed by oxidation with oxygen and catalysis by CuBr. As a result, a series of CMPOs 3 and 3 ' were produced via the cleavage of two bonds (2 C-C) and the formation of three bonds (1 C-N and 2 C-C bonds) in a single step. This protocol can be used to synthesize functionalized CMPOs for combinatorial and parallel syntheses of CMPOs in a one-pot reaction.