Phosphine-Promoted Synthesis of 9 H-Pyrrolo[1,2- a]indole Derivatives via an γ-Umpolung Addition/Intramolecular Wittig Reaction.

The synthesis of substituted 9 H-pyrrolo[1,2- a]indole products from 1 H-indole-2-carbaldehydes and allenoates is described, using a phosphine-promoted Michael addition/intramolecular Wittig reaction. This halide- and base-free methodology provides an efficient access to different tricyclic nitrogen-containing heterocycles (18 examples, 32-88% isolated yields).