Studies on the Efficient Generation of Phosphorus-Carbon Bonds via a Rearrangement of PIII Esters Catalysed by Trimethylhalosilanes

Halotrimethylsilanes Me3SiX (X Bi, I) catalyse rearrangements of tricoordinate phosphorus esters R'R '' P OR into the corresponding phosphoryl systems R'R '' P(O)R. This provides a simple and efficient route to a variety of structures containing phosphorus-carbon bonds, under mild conditions and with good yields. The reaction mechanism wits investigated in detail by P-11 NMR spectroscopy and independent synthesis of the reaction intermediates. It has been demonstrated that the primary products of this catalytic reaction are halogeno P-III struclures R'R"PX and silyl ethers ROSiMe, and that they subsequently react to give the corresponding phosphorus silyl esters-Me3SiOPR'R ''- and alkyl halides RX. At higher temperatures these intermediates then react to form R'R '' P(O)R compounds. This paper also features the surprising observation that when esters (PhPOR)-P-2 and halotrimethylsilanes Me3SiX (X Br, I) are used in 2:1 ratio, phosphonium salts Ph2R2P+X and trimethylsilyl diphenylphosphinate-Ph2P(O)OSiMe3 -are formed as the major products. Experimental evidence indicates that the mechanisms of both reactions are fundamentally different from that of the Michaelis-Arbuzov reaction. Me3SiCl is not reactive and this paper explains why.