Copper(ii)-mediated resolution of α-halo carboxylic acids with chiral O,O′-dibenzoyltartaric acid: spontaneous racemization and crystallization-induced dynamic resolution
作者:Hong-wu Xu、Qi-wei Wang、Jin Zhu、Jin-gen Deng、Lin-feng Cun、Xin Cui、Jun Wu、Xin-liang Xu、Yu-liang Wu
DOI:10.1039/b510170k
日期:——
Herein we present a new example of coordination-mediated resolution of racemic acids by a chiral acid. The reaction of copper(II) acetate monohydrate, optically pure O,Oâ²-dibenzoyltartaric acid (DBTA) and racemic α-bromo-2-chlorophenylacetic acid (HL1) in acetonitrile solution afforded a binuclear copper(II) complex with D-DBTA dianion, α-bromo-2-chlorophenylacetate and acetate as ligands. After decomposition of the complex with acid, the optically active acid ((R)âHL1) was obtained. Similarly, α-bromo-2-fluorophenylacetic acid (HL2), α-bromo-2-bromophenylacetic acid (HL3), α-chloro-2-chlorophenylacetic acid (HL4), α-chloro-2-fluorophenylacetic acid (HL5), α-bromophenylacetic acid (HL6), α-bromo-4-chlorophenylacetic acid (HL7), 2-bromopropionic acid (HL8) and 2-chloropropionic acid (HL9) were resolved by the same method. Satisfactory results were obtained for HL2 to HL5. For HL6 and HL7, only racemic acids were obtained. For the two α-halo aliphatic acids (HL8 and HL9), poor enantioselectivity was obtained. It is more interesting that three acids (HL1, HL2 and HL3) could spontaneously racemize in acetonitrile solution, which resulted in crystallization-induced dynamic resolution (CIDR) with greater than 50% yield.
在此,我们介绍了一种新的手性酸协调介导外消旋酸的拆分方法。乙腈溶液中一水合乙酸铜(II)、光学纯O,O-二苯甲酰酒石酸(DBTA)和外消旋α-溴-2-氯苯乙酸(HL1)的反应产生了二核铜(II)配合物,其中D-DBTA二阴离子、α-溴-2-氯苯乙酸和乙酸为配体。酸分解配合物后,得到光学活性酸((R)-HL1)。类似地,α-溴-2-氟苯乙酸(HL2)、α-溴-2-溴苯乙酸(HL3)、α-氯-2-氯苯乙酸(HL4)、α-氯-2-氟苯乙酸(HL5)、α-溴苯乙酸(HL6)、α-溴-4-氯苯乙酸(HL7)、2-溴丙酸(HL8)和2-氯丙酸(HL9)也通过相同的方法进行了拆分。HL2至HL5获得了令人满意的结果。对于HL6和HL7,只得到了外消旋酸。对于两种α-卤代脂肪族酸(HL8和HL9),得到的对映选择性较差。更有趣的是