| 摘要 |
Prepn. of alpha, alpha-difluoro-beta-silyloxy-1,3-dioxolane-4-propanoic acid thioester derivs. of formula (IV) comprises: (a) contacting an O, S-acetate of formula (II) F2ZC-C(=O)SR4 with a halosilane of formula (III) XSiR1R2R3 in an aprotic solvent provided that when Z is Cl, reaction is in the presence of a reducing agent and at 25-80 deg.C and when Z is H, a base is added and the temp. is -78 to 25 deg.C, to give a 2,2-difluoroketenesilyl O, S-acetal of formula (I); (b) reacting (I) with a glyceraldehyde deriv. of formula (V) at -78 to 80 deg.C provided that a Lewis acid is added when Z is H. In the formulae, R1-R4 are 1-7C alkyl, 3-7C cycloalkyl, Ph, naphthyl or thienyl; R5 and R6 are 1-3C alkyl; or R5 + R6 is (CH2)n; n is 3-6; Z is Cl or H; X is Cl or Br. Step (a) is claimed per se and (I) are new. |
