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. 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.