Access to 4-methylene-phospholenes through BF3·Et2O catalyzed isomerization of 3,4-dimethylphosphole sulfides

Abstract

We have developed a practical synthetic approach to 4-methylene-phospholene derivatives through BF₃·Et₂O-catalyzed isomerization of 3,4-dimethylphosphole sulfides. The reaction simultaneously establishes a P-stereocenter while performing skeletal rearrangement. The transformation is enabled by the weak antiaromatic character of the phosphole sulfides, which facilitates the thermodynamically favoured migration of an endocyclic double bond to the exocyclic terminal position.