Halogenated Olefins as Chain Transfer Agents in the Synthesis of Telechelic Polynorbornenes Using Ruthenium Alkylidene Catalysts. Computational and Experimental Studies

The Open Macromolecules Journal Pub Date : 2008-10-23 DOI:10.2174/1874343900802010032

Joel Vargas, Serguei Fomine, L. Fomina, M. Tlenkopatchev

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引用次数: 3

Abstract

Ring-opening metathesis polymerization (ROMP) of norbornene (NB) and its derivatives N-adamantyl-exo- endo-norbornene-5,6-dicarboximide (AdNDI) and N-cyclohexyl-exo-endo-norbornene-5,6-dicarboximide (CyNDI) in the presence of cis-1,4-dichloro-2-butene (2a) and cis-1,2-dichloro-ethylene (2b) as chain transfer agents (CTAs) using a (1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazolilydene) (PCy3)Cl2Ru=CHPh (I) has been studied. � Halogenated ole- fin 2b shows no activity as a CTA whenhalogenated olefin 2a is readily cross-metathesized with NB and norbornene dicarboximides. The chain transfer reaction pathways during the ROMP of NB to 2b using a (1,3-diphenyl-4,5- dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (1) have been studied at B3LYP/LACVP* level of theory. The calcula- tions show that 2b is a poor substrate for the metathesis reaction due to the steric effect produced by chlorine atoms di- rectly linked to the double bond. The calculated Gibbs free activation energy of a chain transfer reaction from ring-opened NB to 2b was 25.1 kcal/mol.

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卤化烯烃作为链转移剂在烷基化钌催化合成远旋聚降冰片烯中的应用。计算与实验研究

研究了降冰片烯(NB)及其衍生物n -adamantyl-外-内-降冰片烯-5,6-二碳酰亚胺(AdNDI)和n -环己基-外-内-降冰片烯-5,6-二碳酰亚胺(CyNDI)在顺式-1,4-二氯-2丁烯(2a)和顺式-1,2-二氯乙烯(2b)作为链转移剂(cta)下，以(1,3-二(2,4,6-三甲基苯基)-4,5-二氢咪唑苯基)(PCy3)Cl2Ru=CHPh (I)为原料进行开环复分解聚合(ROMP)。当卤代烯烃2a很容易与NB和降冰片烯二酰亚胺交叉反应时，卤代烯烃2b没有表现出作为CTA的活性。在B3LYP/LACVP*的理论水平上研究了(1,3-二苯基-4,5-二氢咪唑-2-酰基)(PCy3)Cl2Ru=CHPh(1)在NB - 2b ROMP过程中的链转移反应途径。计算表明，由于直接与双键相连的氯原子所产生的空间效应，2b是一种不适于复分解反应的底物。从开环NB到2b的链转移反应的吉布斯自由活化能为25.1 kcal/mol。

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The Open Macromolecules Journal

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