作者:Ryszard Bodalski、Stefan Jankowski、Marek L. Glowka、Tomasz Filipiak、Louis D. Quin
DOI:10.1021/jo00097a018
日期:1994.9
Thermolysis of derivatives of the 2,3-oxaphosphabicyclo[2.2.2]octene ring system with phosphorus in the phosphonothionoate state accomplishes the extrusion of O-alkyl metathiophosphates, ROP(S)O, as highly reactive intermediates. With alcohol present, the intermediate is trapped as an O,O-dialkyl phosphorothionoate, (RO)(R'O)P(S)OH. With R = (RS)-sec-butyl in the metathiophosphate released, the phosphorothionoate is formed as a 1:1 mixture of diastereoisomers, but when R = (RS)-1-methoxy-2-propyl in the metathiophosphate, a 4:1 isomer mixture is formed in CHCl3, and 2:1 in toluene. This can be explained by anchimeric participation of the methoxy group, giving diastereoisomeric 1,3,2-dioxaphospholane intermediates in amounts that are unequal due to small stability differences that arise from steric effects. The structure of the bicyclic precursor was established by X-ray diffraction analysis and led to the prediction that the major isomer would have the R*(c),S*(p) configuration. This was proved by an independent synthesis of the same 1:1 isomer mixture from thionation of (RO)PH(O)(OR'), separation by chromatography, and X-ray diffraction analysis of the dicyclohexylamine salt of one of the isomers. This isomer had the R*(c),R*(p) configuration and was identical to the minor isomer (with the more upfield P-31 NMR signal) obtained from the metathiophosphate.