Alkylations Using Methyltrialkoxyphosphonium Tetrafluoroborate Salts. Synthetic and Mechanistic Aspects of Methyl, Ethyl, 2-Propyl, and 2-Octyl Group Transfers

Article abstract of DOI:10.1021/jo00199a026

Trialkyl phosphites, (RO)3P for R = methyl, ethyl, 2-propyl, and 2-octyl, were alkylated with Meerwein's salt (Me3O+BF4-) to yield the corresponding trialkoxymethylphosphonium tetrafluoroborate salts.These salts, which are all molten at room temperature, were reacted neat or in solvents with a series of nucleophiles.Thus, a variety of O, N, S, and halogen nucleophiles reacted by substitution at the R group C-O bond to give high yields after a trivial workup procedure.Rates of reaction were measured for substituted benzoic acids (4-XC6H4CO2H; X= CH3, t-Bu, CH3O, H, CF3, CN, NO2) with the neat salts under pseudo-first-order conditions or with the salt in CH3CN under second order conditions.The resulting Hammett plots indicate very little change in sensivity to the substituents when R = isopropyl compared with R = methyl and when the salt itself instead of CH3CN is solvent.