Synthesis, Conformational Stability, and Asymmetric Transformation of Atropisomeric 1,8-Bisphenolnaphthalenes
作者:Marwan W. Ghosn、Christian Wolf
DOI:10.1021/jo200309g
日期:2011.5.20
Highly congested, axially chiral 1,8-bisphenolnaphthalenes have been synthesized in 75% overall yield by palladium-catalyzed Suzuki coupling of 1,8-diiodonaphthalene and 4-methoxy-2-methylphenylboronic acid followed by regioselective formylation and deprotection. The C2-symmetric anti-stereoisomers of 1,8-bis(2′-methyl-4′-hydroxy-5′-formylphenyl)naphthalene, 5, and its diimine analogues 9 and 10 were
通过钯催化的1,8-二碘萘与4-甲氧基-2-甲基苯基硼酸的Suzuki偶联,然后进行区域选择性的甲酰化和脱保护,已合成了高度拥挤的轴向手性1,8-双酚萘,其总产率为75%。发现1,8-双(2'-甲基-4'-羟基-5'-甲酰基苯基)萘5及其二亚胺类似物9和10的C 2对称抗立体异构体比苯丙胺更稳定。相应的顺式异构体。晶体学分析表明,这种立体化学偏好是由独特的分子内氢键基序和随之而来的空间排斥最小化引起的。三芳基5证明在室温下能绕手性轴稳定旋转,并且通过与(R)-2-氨基-1-丙醇和(R)-2-氨基-3-甲基-1-丁醇形成非对映体二亚胺来分离对映异构体分别进行色谱分离和温和水解。慢顺/反的-interconversion 5,9,和10在增强的温度下观察和diastereomerization和enantiomerization过程是由CD和NMR光谱监测。吉布斯活化能,Δ ģ ⧧,为的异构化5被确定为103