Synthesis and thermal stability of silicon-containing esters of phosphorus acids 5.* the relative migration ability of substituents at the silicon atom in the thermal rearrangement of trialkylsilylmethyl diphenyl phosphates

Article abstract of DOI:10.1007/BF02495692

A number of trialkylsilylmethyl diphenyl phosphates MeRR'SiCH₂OP(O)(OPh)₂ (Ia-e: R = Et (a), Pr (b), CF₃CH₂CH₂ (c, e), Me₃SiCH₂ (d); R' = Me (a-d), Et (e)) were synthesized and their thermal rearrangement, of the 1,2-shift type, was studied. The rearrangement consists of the migration of an alkyl group from Si atom to the methylene carbon atom and gives the corresponding silyl esters. The rate of the rearrangement was found to increase in the order 1d < 1b < 1a < 1 (R = R' = Me) < 1c corresponding to the enhancement of the total inductive effect (-I) of the substituents at the Si atom. The relative migration ability of the substituents at the Si atom, determined by GC/MS analysis of the disiloxane fraction resulting from hydrolysis of pyrolyzed phosphates 1a-e, increases in the order R = Pr < Et < CF₃CH₂CH₂ < Me Me₃SiCH₂, which differs substantially from the order in which the rate of the rearrangement of phosphates 1a-d changes. The electro-negativity of the migrating group affects noticeably the relative ability to migrate.