An access to original 3,3-bis(phospholyl)lactones

The reaction of lithium 3,4-dimethylphospholide with dicarboxylic acid dichlorides yields the original 3,3-bis(3,4-dimethylphospholyl)lactones via an unexpected cyclization reaction. One of the products has been characterized by X-ray crystal structure analysis of its bis(pentacarbonylmolybdenum) complex.