KINETICS OF THE METHYL-IODIDE CATALYZED AND AUTOCATALYZED ARBUZOV REARRANGEMENT (METHOXYPHOSPHONIUM, CONDUCTIVITY, PHOSPHORUS NMR)

[摘要] Rates for the two sequential steps of the Arbuzov rearrangement: (UNFORMATTED TABLE FOLLOWS)MeIABPOMe(--->)ABP(O)Me, A, B, = OMe, OMe;(TABLE ENDS)OMe, Ph; Ph, Ph; OMe, Et; and Et, Et were measured by conductivity. The concentration of the methoxyphosphonium iodide intermediates was determined from calibration curves relating conductivity to concentration for the analogous stable ethylphosphonium iodides.No significant contribution from the autocatalytic Arbuzov rearrangement: (UNFORMATTED TABLE FOLLOWS)ABP('+)(OMe)MeABPOMe(--->)ABP(O)Me,(TABLE ENDS)was observed for these reactions. For all cases except methyl diethyl- phosphinite (A = B = Et), the rate determining step is the alkylation of the trivalent phosphorus ester. Rates for the autocatalytic Arbuzov rearrangement of the same compounds were measured by ('31)P nmr. The substituent effect ((rho)(,I)) for the reactions was determined by correlation of the kinetic data with the sum of the Taft inductive parameters ((sigma)(,I)) of the substituents on phosphorus. The (rho)(,I) values for the two steps of the ;;textbook;; Arbuzov rearrangement are -4.6 and 5.6 respectively. The (rho)(,I) for the autocatalytic Arbuzov rearrangement is 0.75.

[发布机构] Rice University

[效力级别] chemistry