One-Pot Synthesis of Poly(vinyl alcohol) (PVA) Copolymers via Ruthenium Catalyzed Equilibrium Ring-Opening Metathesis Polymerization of Hydroxyl Functionalized Cyclopentene
One-Pot Synthesis of Poly(vinyl alcohol) (PVA) Copolymers via Ruthenium Catalyzed Equilibrium Ring-Opening Metathesis Polymerization of Hydroxyl Functionalized Cyclopentene
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羟基功能化环戊烯钌催化平衡开环复分解聚合一锅法合成聚乙烯醇（PVA）共聚物
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发表时间：
2014
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通讯作者：
R. Grubbs
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作者：
Róbert Tuba;M. Al‐Hashimi;Hassan S. Bazzi;R. Grubbs
以无保护的3-环戊烯-1-醇(2)和1，6-庚二烯-4-醇(2)为原料，用(1，3-bis(2，4，6-trimethylphenyl)-2-midazolidinylidene)dichloro(phenylmet(三环己基膦)Ru(6)和(1，3-bis(2，4，6-trimethylphenyl)-2-imidazolidinylidene)dichloro(o-isoprop-O-苯亚甲基(7)Ru(7)为催化剂，通过平衡开环歧化聚合(ROMP)或非环二烯歧化(ADMET)一锅反应合成了具有良好结构的聚乙烯醇-丙二烯(4)。测定了ΔH=-6.2kcal mol^(-1)和ΔS=-18.9calmol^(-1)K^(-1)的平衡活化热和活化熵。观察到的热力学参数得到了计算研究的支持。计算得到的2(-6.8kcal·mol~(-1))的环应变能与6和7催化的平衡ROMP反应的活化能相当。顺式：反式烯键比分析表明，顺式：反式选择性为20：80。4的加氢反应得到了高产率的聚乙烯醇-丙交酯(11)。由于环戊烯(1)和环戊烯(2)具有相似的环应变能，平衡共聚导致聚合物具有随机分布的二元体。一般来说，这意味着形成的聚合物含有大约50%的交替聚合物、25%3和25%4的均聚物二元，如随机聚合所预期的那样。
Well-defined poly(vinyl alcohol-alt-propenylene) (4) was synthesized in one-pot reaction via equilibrium ring-opening metathesis polymerization (ROMP) or acyclic diene metathesis (ADMET) of nonprotected 3-cyclopentene-1-ol (2) and 1,6-heptadiene-4-ol using (1,3-bis(2,4,6-trimethylphenyl)-2-midazolidinylidene)dichloro(phenylmet hylene)(tricyclohexylphosphine)ruthenium (6) and (1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(o-isoprop oxyphenylmethylene)ruthenium (7) metathesis catalysts. The activation enthalpy and entropy of the equilibrium ROMP were determined as ΔH = -6.2 kcal mol^(-1) and ΔS = -18.9 cal mol^(-1) K^(-1). The observed thermodynamic parameters were supported by computational studies. The calculated ring strain energy for 2 (-6.8 kcal mol^(-1) is comparable with the observed activation enthalpy for its equilibrium ROMP reaction catalyzed by 6 or 7. The cis:trans olefinic bond ratio analysis indicated a 20:80 cis:trans selectivity. The hydrogenation of 4 resulted in poly(vinyl alcohol-alt-propylene) (11) in high yield. Because of the similar ring strain energies of cyclopentene (1) and 2, the equilibrium copolymerization results in a polymer having randomly distributed dyads. In general, it means that the polymer formed contains approximately 50% alternating polymer, 25% 3, and 25% 4 homopolymer dyads as expected for a random polymerization.