Pd-catalyzed polymerization of dienes that involves chain-walking isomerization of the growing polymer end: synthesis of polymers composed of polymethylene and five-membered-ring units.
Pd-catalyzed polymerization of dienes that involves chain-walking isomerization of the growing polymer end: synthesis of polymers composed of polymethylene and five-membered-ring units.
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DOI：
10.1002/anie.200701630
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发表时间：
2007-08
影响因子：
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通讯作者：
T. Okada;Sehoon Park;Daisuke Takeuchi;K. Osakada
中科院分区：
文献类型：
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作者：
T. Okada;Sehoon Park;Daisuke Takeuchi;K. Osakada
乙烯与降冰片烯和环戊烯等环状烯烃以及与在聚合物生长过程中发生环化的 1, 5-或 1, 6-二烯发生共聚反应，产生具有随机分布的五元或六元环状单元的烃类聚合物。 [1]这些使用带有官能团的共聚单体并由后过渡金属配合物催化的反应提供了制备官能化聚乙烯的稳定途径。使用 Ni 络合物催化的 5-降冰片烯-2-甲酸乙酯的反应可得到具有随机分布的 CO2Et 基团的聚乙烯，[2]，而钴络合物催化的乙烯与 2-(4-甲氧基苯基)-1-亚甲基环丙烷的交替共聚可产生具有 C6H4OMe 基团的聚合物。 [3]最近，我们成功实现了乙烯与二烯丙二酸异亚丙基酯的无规共聚，得到了带有酯基的五元环单元的聚合物。 [4]尽管上述无规共聚可以通过改变所用两种单体的摩尔比来调节聚合物链上官能团的平均密度，但它不适合聚合物结构的精确设计。在此，我们报道了具有末端和内部 C= C 键的 1, 6-二烯经历了 Pd 配合物促进的环聚合，并伴随着聚合物的链行走，[5, 6]，并在官能化五元环之间提供具有所需长度的 (CH2) n 间隔基的聚合物。四种 Pd 配合物 1a-1d 用作本研究中使用的催化剂的前体（图 1）。由1a和四(3, 5-双(三氟甲基)苯基)硼酸钠(NaBArF4)制备的催化剂在室温下引发异亚丙基烯丙基(巴豆基)丙二酸酯(I-1)在室温下环化聚合，生成聚合物-(CH2-C5H6(C5H6O4)-CH2CH2)m-(poly-I-1)，如式(1)所示表 1（条目 1）。图2a显示了聚合物的13C{1H}NMR谱。五元环中 CH 和 CH2 碳原子的信号分别出现在 δ= 46.9 和 45.8 ppm 处，
Co-polymerization reactions of ethylene with cyclic olefins, such as norbornene and cyclopentene as well as with 1, 5-or 1, 6-dienes that undergo cyclization during the polymer growth, produce hydrocarbon polymers with five-or sixmembered cyclic units that are located randomly.[1] These reactions that use a co-monomer with a functional group and are catalyzed by late-transition-metal complexes provide a steady route to functionalized polyethylenes. The reaction using ethyl 5-norbornene-2-carboxylate catalyzed by a Ni complex affords polyethylene with the CO2Et groups located randomly,[2] whereas an alternating co-polymerization of ethylene with 2-(4-methoxyphenyl)-1-methylenecyclopropane catalyzed by a cobalt complex yields a polymer with C6H4OMe groups.[3] Recently, we have succeeded in the random co-polymerization of ethylene with isopropylidene diallylmalonate, and obtained a polymer with five-membered cyclic units with ester groups.[4] Although the above random co-polymerization could regulate the averaged densities of the functional group along the polymer chain by changing the molar ratio of the two monomers used, it is not suited for the precise design of the polymer structure. Herein, we report that 1, 6-dienes with both terminal and internal C= C bonds undergo a Pd-complex-promoted cyclopolymerization accompanied by the chain walking of the growing polymer,[5, 6] and afford polymers with (CH2) n spacers of the desired length between the functionalized five-membered rings. The four Pd complexes 1a–1d were used as the precursors of the catalysts used in this study (Figure1). A catalyst prepared from 1a and sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate)(NaBArF4) initiates the cyclopolymerization of isopropylidene allyl (crotyl) malonate (I-1) at room temperature to produce the polymer-(CH2-C5H6 (C5H6O4)-CH2CH2) m-(poly-I-1), as shown in Equation (1) and Table 1 (entry 1). Figure 2a shows the 13C {1H} NMR spectrum of the polymer. Signals of the CH and CH2 carbon atoms in the fivemembered ring appear at δ= 46.9 and 45.8 ppm, respectively,