3′,4′,5′-三氟联苯-4-硼酸的合成及表征

Synthesis and characterization of 3',4',5'-trifluorobiphenyl-4-boronic acid

使用工业上易得的原料通过3步反应合成标题化合物。苯硼酸与3,4,5-三氟溴苯作为起始原料,在K2CO3水溶液和甲苯体系中,Pd/C催化反应生成3,4,5-三氟联苯,产率80%。接着3,4,5-三氟联苯在CCl4中经过Fe+I2催化溴化得到4′-溴-3,4,5-三氟联苯,产率75%。4′-溴-3,4,5-三氟联苯与n-BuLi在-78℃下反应生成3′,4′,5′-三氟联苯-4-锂,然后与硼酸三正丁酯-78℃反应,最后在室温下酸性条件下水解生成目标产物,产率86%。合成路线的总收率达到51.6%。合成的化合物用元素分析、FT-IR、1HNMR和13CNMR等手段进行了表征。

3＇,4＇,5＇-Trifluorobiphenyl-4-boronic acid was synthesized via a three-step reaction process with commercially available materials.Phenylboronic acid and 3,4,5-trifluorobromobenzene were used as starting materials under the catalytic action of Pd/C in a system composed of K2CO3 solution and toluene to give a biaryl intermediate 3,4,5-trifluorobiphenyl in 80% yield.Then 3,4,5-trifluorobiphenyl was exclusively brominated by Br2 in CCl4 in the presence of Fe＋I2 catalysts to give 4＇-bromo-3,4,5-trifluorobiphenyl in 75% yield.4＇-Bromo-3,4,5-trifluorobiphenyl then reacted with n-BuLi to give（3＇,4＇,5＇-trifluorobiphenyl-4-）lithium at-78 ℃,which was then boronylated by B（O-nBu）3 at the same temperature and hydrolyzed by acid at room temperature to give the desired compound in 86%.The total product yield was up to 51.6%.The synthesized product was characterized by elemental analysis,FT-IR,1HNMR and 13CNMR,respectively.