Synthesis of Indolizine and Pyrrolo[1,2-a]azepine Derivatives via a Gold(I)-Catalyzed Three-Step Cascade

Linear N-alkenyl or alkynyl N-sulfonyl 1-aminobut-3-yn-2-ones are converted into bicyclic indolizines and pyrrolo[1,2-alpha]azepine-type alkaloids upon gold(I) catalysis (17 examples, 10-85%). The reaction cascade allowed formation of C-N, O-S, and C-C bonds via a cycloisomerization/sulfonyl migration/cyclization process using 10 mol % of [(2-biphenyl)di-tert-butylphosphine]gold-(I) triflimide complex in dichloromethane.