Polyhydroxyoligothiophenes. 2. Hydrogen-Bonding-Oriented Solid State Conformation of 3,3'-Bis(2-hydroxyethyl)-2,2'-bithiophene and Regioselective Synthesis of the Corresponding Head-to-Head/Tail-to-Tail Quater- and Sexithiophene.
Polyhydroxyoligothiophenes. 2. Hydrogen-Bonding-Oriented Solid State Conformation of 3,3'-Bis(2-hydroxyethyl)-2,2'-bithiophene and Regioselective Synthesis of the Corresponding Head-to-Head/Tail-to-Tail Quater- and Sexithiophene.
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聚羟基低聚噻吩。
DOI：
10.1021/jo952278t
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
L. Antolini
中科院分区：
文献类型：
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作者：
G. Barbarella;M. Zambianchi;A. Bongini;L. Antolini
本文报道了用于合成头-头/尾-尾2-羟乙基取代的低聚噻吩的结构单元3，3 '-双（2-羟乙基）-2，2'-联噻吩（1）的X-射线结构。与迄今为止报道的所有bithiophenes相反，1表现出非共面反构象和环间扭转角（67.5度），这是有史以来测量的α-共轭oligothiophenes相邻环中最大的。这种不寻常的构象似乎是由涉及OH基团的分子间氢键相互作用决定的，OH基团将分子结合在紧密堆积的层中。本文还描述了1的二聚体和三聚体的区域选择性合成，即3，3 '，4”，3“'-四（2-羟乙基）-2，2 '：5'，2”：5”，2“'-四噻吩（3c）和3，3'，4”，3“'，4”"，3”“'-六（2-羟乙基）-2，2 '：5'，2”：5”，2”“'-六噻吩（4 b）。3c和4 b通过钯（0）催化的1的四氢吡喃基衍生物的单-和二锡烷与适当的单溴化合物的偶联（Stille反应）获得。最后，报告力场计算表明，1，3C，和4 B测量的低λ（最大）值也是分子内氢键相互作用的结果，有利于在溶液中高度扭曲的构象。
This paper reports the X-ray structure of 3,3'-bis(2-hydroxyethyl)-2,2'-bithiophene (1), which is the building block for the synthesis of head-to-head/tail-to-tail 2-hydroxyethyl-substituted oligothiophenes. Contrary to all the bithiophenes reported so far, 1 exhibits a noncoplanar anti conformation and an inter-ring twist angle (67.5 degrees ) which is the largest ever measured for adjacent rings of alpha-conjugated oligothiophenes. This unusual conformation appears to be dictated by intermolecular hydrogen-bonding interactions involving the OH groups, which bind the molecule in close packed layers. The paper also describes the regioselective synthesis of the dimer and the trimer of 1, namely of 3,3',4",3"'-tetrakis(2-hydroxyethyl)-2,2':5',2":5",2"'-quaterthiophene (3c) and of 3,3',4",3"',4"",3""'-hexakis(2-hydroxyethyl)-2,2':5',2":5",2"':5"',2"":5"",2""'-sexithiophene (4b). 3c And 4b were obtained through palladium(0)-catalyzed coupling of the mono- and distannanes of the tetrahydropyranyl derivative of 1 with the appropriate monobromo compound (Stille's reaction). Finally, the paper reports force-field calculations which suggest that the low lambda(max) values measured for 1, 3c, and 4b are also the result of intramolecular hydrogen-bonding interactions which favor highly twisted conformations in solution.