THERMAL RETRO-TRIMERIZATION OF SOME 1,3,5,2,4,6-TRIOXATRIPHOSPHORINANES TO PHOSPHENITES

Pyrolysis in a packed tube of the vapor from three -tris(aryloxy)-1,3, 5,2,4,6-trioxatriphosphorinanes was performed at 300-350 degrees C and 10(-6) mm; the product was collected on a cold finger chilled by liqu id nitrogen. The cracking of the trimer was complete, and the product at -195 degrees C appeared to consist only of the monomeric aryl phosp henite, ArOP=O. On warming, dimerization occurred, later followed by t rimer formation. The weak P-31 MMR signal for the phosphenite (about d elta 238 for three O-aryl derivatives) persisted in the solution for s everal weeks if water was rigorously excluded. Treatment of the phosph enite with water or alcohols at -195 degrees C gave a mixture of produ cts; the major product (ArO-PH(O)OH) came from addition of the nucleop hile to the P=O bond, but significant amounts (10-20%) of dialkyl H-ph osphonates (HP(O)(OR)(2)) were present, apparently from displacement o f the O-aryl substituent of the phosphenite, followed by addition to t he double bond.