Unprecedented CP systems: Me3SiX (X=Br, I) catalyses rearrangements of PIII esters R′R′′POR into the corresponding phosphoryl systems, providing a simple, mild and efficient route to a variety of structures containing PC bonds. The mechanism has been found to be fundamentally different from that of the Arbuzov–Michaelis reaction and includes three definite steps a, b and c (see scheme).
Halotrimethylsilanes Me3SiX (X=Br, I) catalyse rearrangements of tricoordinate phosphorus esters R′R′′POR into the corresponding phosphoryl systems R′R′′P(O)R. This provides a simple and efficient route to a variety of structures containing phosphoruscarbon bonds, under mild conditions and with good yields. The reaction mechanism was investigated in detail by 31P NMR spectroscopy and independent synthesis of the reaction intermediates. It has been demonstrated that the primary products of this catalytic reaction are halogeno PIII structures R′R′′PX and silyl ethers ROSiMe3 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 Ph2POR 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.