Synthesis of 1,2,3-Trisubstituted Indolizines, Pyrrolo[1,2-a]quinolines, and Pyrrolo[2,1-a]isoquinolines from 1,2-Allenyl Ketones

An efficient synthesis of substituted indolizine and its benzo derivatives, pyrrolo[1,2-a]quinolines and pyrrolo[2,1-a]isoquinolines, by the reaction of allenyl ketones with alpha-bromo carbonyl compounds and pyridines (quinoline or isoquinoline) under mild conditions without an added oxidant other than molecular oxygen from air was developed. Notably, allenyl ketones with or without a substituent attached to the internal position of the allene moiety afforded indolizine derivatives with different substitution patterns.