THE NATURE AND CONSEQUENCES OF THE INTERACTION OF PHOSPHORYL NUCLEOPHILES WITH A TRIORGANOSILYL CHLORIDE

Article abstract of DOI:10.1016/0022-328X(85)80120-0

In order to throw light on the possible role of positively charged tetra-coordinate silicon intermediates in the racemization of α-NpPhMeSiCl (1) induced by uncharged nucleophiles two sets of kinetic studies have been carried out.In the first the rates of two reactions namely racemization of 1 catalysed by (PhO)2(Me3SiO)P=O (2) and transsilylation of 2 with 1, which take place together and are believed to involve the same intermediate were determined; the transsilylation was found to be faster than the racemization, and involved transient formation of an optically active product.In the second the racemization of 1 catalysed by HMPT in various CCl4/CH2Cl2 mixtures was studied; the rate was found to increase markedly with increase in the dielectric constant of the medium.The results of both sets of experiments were consistent with a mechanism involving a silyloxyphosphonium cation intermediate.