as isomeric mixtures by the zinc-mediated coupling reaction of dibromo-fluoroacetate with aldehydes at -20 °C, were successively treated with trimethylaluminium at -15 °C for 0.5 h and with tributyltin hydride in the presence of a catalytic amount of triethylborane at -15 °C for 4 h or at -78 °C for 6 h to give preferentially the threo-isomers of the corresponding α-fluoro-β-hydroxy esters in good
α-
溴-α-
氟-β-羟基酯,通过
锌介导的二
溴-
氟乙酸酯与醛在 -20 °C 下的偶联反应制备为异构混合物,在 -15 °C 下连续用
三甲基铝处理 0.5 小时,然后在催化量的三乙基
硼烷存在下与三丁基氢化
锡在 -15 °C 下反应 4 小时或在 -78 °C 下反应 6 小时,以高产率优先得到相应 α-
氟-β-羟基酯的苏式异构体.