Organocatalytic C3-functionalization of indolizines: synthesis of biologically important indolizine derivatives

A Bronsted acid-catalyzed C3-alkylation of indolizines has been established with different electrophiles such asortho-hydroxybenzyl alcohols, other precursors ofpara-quinone methides andortho-quinone methides, and 2-indolylmethanol as well. By using this approach, a series of C3-functionalized indolizines were synthesized in overall good yields (up to 89%). These examples demonstrate that the Bronsted acid-catalyzed C3-alkylation of indolizines has a wide applicability, which can serve as a useful method for synthesizing C3-functionalized indolizine derivatives with structural diversity. This reaction has fulfilled the task of developing organocatalytic C3-functionalization of indolizines for the synthesis of biologically important indolizine derivatives.