Cycloaromatization approach to polysubstituted indolizines from 2-acetylpyrroles: decoration of the pyridine unit.

A new synthetic route to indolizines with various substituents on the pyridine moiety was developed by utilizing a facile cycloaromatization of 2-acetylpyrrole derivatives. Without isolation, the resulting intermediates were allowed to react with various electrophiles to afford a range of indolizines. In particular, Suzuki-Miyaura cross-coupling of O-triflates with (hetero)arylboronic acids permitted introduction of diverse substituents at the C8 position of an indolizine skeleton.