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.
An efficient method for the diastereoselective synthesis of α-fluoro-β-hydroxy esters based on the radical reduction of α-bromo-α-fluoro-β-hydroxy esters
−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, the corresponding threo-α-fluoro-β-hydroxyalkanoates were obtained highly diastereoselectively in good yields. On the other hand, the α-bromo-β-hydroxy esters having an aromatic substituent were subjected to the reaction with tris(trimethylsilyl)silane in the presence of a catalytic amount
Highly Stereoselective Radical Reduction of α-Bromo-α-fluoro-β-hydroxy Esters with Tributyltin Hydride Leading to<i>threo</i>-α-Fluoro-β-hydroxy Esters
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 tributyltinhydride 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.