New route synthesis of indolizines via 1,3-dipolar cycloaddition of pyridiniums and alkynes

A convenient synthesis of 2,3-di and 1,2,3-trisubstituted indolizines has been achieved via a 1,3-dipolar cycloaddition of pyridiniums and alkynes. Various alkynes and diynes were used instead of dimethyl acetylenedicarboxylate (DMAD) and its analogues in the traditional method. The corresponding 1,2,3-trisubstituted indolizines are useful building blocks for the construction of complex indolizine derivatives.