Thermal Retro-Trimerization of Some 1,3,5,2,4,6-Trioxatriphosphorinanes to Phosphenites

Article abstract of DOI:10.1021/jo00121a042

Pyrolysis in a packed tube of the vapor from three 2,4,6-tris(aryloxy)-1,3,5,2,4,6-trioxatriphosphorinanes was performed at 300-350 deg C and 1E-6 mm; the product was collected on a cold finger chilled by liquid nitrogen.The cracking of the trimer was complete, and the product at -195 deg C appeared to consist only of the monomeric aryl phosphenite, ArOP=O.On warming, dimerization occured, later followed by trimer formation.The weak 31P NMR signal for the phosphenite (about δ 238 for three O-aryl derivatives) persisted in the solution for several weeks if water was rigorously excluded.Treatment of the phosphenite with water or alcohols at -195 deg C gave a mixture of products; the major product (ArO-PH(O)OH) came from addition of the nucleophile to the P=O bond, but significant amounts (10-20percent) of dialkyl H-phosphonates (HP(O)(OR)2) were present, apparently from displacement of the O-aryl substituent of the phosphenite, followed by addition to the double bond.