Reaction of Phosphole Sulfides with Diazoalkanes as a New Route to Phosphinines

Article abstract of DOI:10.1021/jo00012a042

The reaction of ethyl diazoacetate with 1-(methylthio)-3,4-dimethylphosphole 1-sulfide (6) in refluxing xylene leads to the corresponding diene-carbene <2+1> cycloadduct 7.The stereochemistry of 7 was established by X-ray crystal structure analysis.Compound 7 is converted into 2-(ethoxycarbonyl)-4,5-dimethylphosphinine (4) upon reaction with triphenyl phosphite at 160 deg C.On the basis of the X-ray data, the proposed mechanism includes the opening of the cyclopropane ring of 7 with selective phosphorus-assisted migration of the ethoxycarbonyl group.This kind of chemistry can be transposed to a 2,2'-biphosphole to prepare a 2,2'-bisphosphinine.