HIGHLY REGIOSELECTIVE AND STEREOSPECIFIC FUNCTIONALIZATION OF 1,2-PROPANEDIOL WITH TRIMETHYL(X)SILANES EMPLOYING THE 1,3,2-LAMBDA-5-DIOXAPHOSPHOLANE METHODOLOGY

The regioselective ring opening of (S)-4-methyl-2,2,2-triphenyl-1,3,2-lambda-5-dioxaphospholane (2) [prepared from the bis(transoxyphosphoranylation) of (S)-1,2-propanediol (1) with diethoxytriphenylphosphorane (DTPP)] was initiated with several trimethylsilyl reagents (Me3SiX: X = PhS, I, Br, Cl, CN, and N3) to afford the regioisomeric (silyloxy)phosphonium salts. A stereospecific extrusion of triphenylphosphine oxide from these oxyphosphonium salts gave predominantly the thermodynamically less stable C-2-X-substituted derivatives with nearly complete inversion of stereochemistry at the C-2 stereogenic center (i.e., X = PhS).