Phospholanes via Twofold C-H-Addition to Phospholes

A synthetic route towards phospholanes via twofold C−H-addition of a DMSO molecule to β-H substituted phospholes is described. The resulting fused phospholane oxothiolane system in case of symmetric α-substitution possesses four stereogenic centers or rather six in case of asymmetric α-substitution. The reaction conditions are shown to be applicable for a variety of phospholes with different P- or α-substituents always leading to stereoselective formation of the fused heterocyclic ring system. All phospholane derivatives with one exception are sufficiently air stable for purification with column chromatography and are fully characterized by NMR and elemental analysis and mass spectrometry. With the help of X-ray crystallography, the different configurations of the isomers could be demonstrated. For one model system derivatization reactions are presented. When oxidizing or reducing the sulfoxide group only a single diastereomer is observed.