RESTRICTED ROTATION IN HEXAARYLBENZENES
RESTRICTED ROTATION IN HEXAARYLBENZENES
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DOI：
10.1021/ja00463a034
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发表时间：
1977-01-01
影响因子：
15
通讯作者：
GUST, D
中科院分区：
文献类型：
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作者：
GUST, D
在核磁共振时间尺度上，六芳基苯以外围环垂直于中心环平面的构象存在。在环的邻位或Meta位取代的六芳基苯，其中心环和环之间的单键旋转受限，产生复杂的立体异构和立体异构行为。观察到的旋转势垒相对较高（高达~ 38 kcal/mol），甚至只带有间甲基取代基的环也会导致~ 16 kcal/mol的势垒。最近对三芳基甲烷、2四芳基乙烷3和相关体系2· 4中扭转异构现象的研究表明，适当取代的六芳基苯也可能表现出受限的旋转。如果能合成出具有较高旋转位阻的取代六芳基苯，将产生一个具有丰富立体化学特征的分子体系。这里报告的是一项初步研究的结果，表明这确实是
Hexaarylbenzenes exist in a conformation in which the peripheral rings are perpendicular to the plane of the central ring on the nmr time scale. Hexaarylbenzenessubstituted in ortho or meta positions of the peripheral rings display restricted rotation aboutthe single bonds joining the central and peripheral rings, and complex stereoisomerism and stereoisomerization behavior results. The rotational barriers observed are relatively high (up to~ 38 kcal/mol), and even rings bearing only a m-methyl substituent lead to barriers of~ 16 kcal/mol.Recent studies of torsional isomerism in triarylmethanes, 2 tetraarylethanes, 3 and related systems2· 4 suggested that suitably substituted hexaarylbenzenes might also demonstrate restricted rotation. If substituted hexaarylbenzenes having relatively high barriers to rotation about thebonds connecting the peripheral and central aromatic rings could be synthesized, a molecular system possessing a rich variety of interesting stereochemical features would result. Reported here are the results of an initial study demonstrating that this is indeed the