Synthesis of Pentasubstituted 2-Aryl Pyrroles from Boryl and Stannyl Alkynes via One-Pot Sequential Ti-Catalyzed [2+2+1] Pyrrole Synthesis/Cross Coupling Reactions

An efficient catalytic synthesis of 2-heteroatom-substituted (9-BBN or SnR3) pyrroles via Ti-catalyzed [2+2+1] heterocoupling of heteroatom-substituted alkynes is reported. The resulting 2-boryl substituted pyrroles can then be used in Suzuki reactions in a 1-pot sequential fashion, resulting in pentasubstituted 2-aryl pyrroles that are inaccessible via previous [2+2+1] heterocoupling strategies.