Synthesis of Asymmetric 4H-1, 3, 2-Benzodioxaphosphorin 2-Sulfides from Intramolecular Cyclization Reaction

Asymmetric 6-substituted-2-methoxy-4-(2,4-dichlorophenyl)-4H,3,2-benzodioxa-phosphorin 2-sulfides were prepared tyom intramolecular cyclization. The diastereomers wereseparated by column chromatography and fractional crystallization. Their structures werecharacterized on the basis of 1 H NMR. 31 P NMR and x-ray diffraction analysis.