Synthesis of indolizine derivatives utilizing [1,2]-phospha-brook rearrangement/cycloisomerization sequence

A new synthesis of indolizine derivatives was developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. The method involves the generation of allenylpyridine from alkynyl 2-pyridyl ketones through the [1,2]- phospha-Brook rearrangement and the following cycloisomerization without using transition-metal catalysts. The method can be performed in a one-pot fashion and directly provides indolizine derivatives having a phosphate moiety that can function as a handle for further manipulation.