Organosilicon compounds. Part XXXVII. Optical resolution of p-(ethylmethylphenylsilyl)benzoic acid

Abstract

p-(Ethylmethylphenylsilyl)benzoic acid, m. p. 99·5°, was prepared, and resolved by fractional crystallisation of its (–)-quinine salt from ethanol. The least soluble diastereoisomer yielded the (+)-acid, m. p. 99·5°, [α]_D²⁰+ 2·75°(c 2·8 in benzene), and from the mother-liquors was obtained the optically impure (–)-acid, m. p. 99·5°, [α]_D²⁰–1·65°(c 3·2 in benzene). No racemisation occurred when the (+)-acid was kept for 6 hours as a liquid at 100° or for 25 hours in solution in aqueous-methanolic potassium hydroxide at room temperature.

The preparations of, and attempted resolution of, some of the following compounds (R = Et or Prⁱ) are described: MeR(EtO)Si·C₆H₄·NMe₂-p, p-[MeR(EtO)Si]·C₆H₄·NMe₃⁺l^–, p-[MeR(HO)Si]·C₆H₄·NMe₃⁺l^–, BuⁿMePrⁱSiCl, BuⁿMePrⁱSiOBu^s, EtMe(p-Me·C₆H₄)SiF, and p-(MeF₂Si)·C₆H₄·CO₂H.