Palladium(II)-Catalyzed Rearrangement and Oligomerization Reactions of cis-Bicyclo[4.2.0]oct-7-ene
Palladium(II)-Catalyzed Rearrangement and Oligomerization Reactions of cis-Bicyclo[4.2.0]oct-7-ene
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DOI：
10.1021/om200877p
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发表时间：
2012-02-13
期刊：
影响因子：
2.8
通讯作者：
Tritto, Incoronata
中科院分区：
文献类型：
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作者：
Curran, Katherine;Risse, Wilhelm;Tritto, Incoronata
在几种Pd（II）催化剂存在下，顺式双环[4.2.0]辛-7-烯（4a）发生烯烃异构化（“环行走”）和低聚化，分别生成顺式双环[4.2.0]辛-2-烯（4d）和低分子量脂环族低聚物5a-d。所研究的催化剂为[Pd（NCEt）（4）][BF_4]（2）（1）、[（eta（3）-烯丙基）Pd（solv）（2）][SbF_6]（2; solv = CH_2Cl_2）、[（1，10-菲咯啉）Pd（CH_3）（NC-（CH_2）（6）CH_3）][SbF_6]（6）和[（2，9-二甲基-1，10-菲咯啉）Pd（CH_3）（NC（CH_2）（6）CH_3）][SbF_6]（7）。异构化包括形成4d和5a-d的烯属端基，并且范围为使用催化剂7的94%至使用催化剂2的29%。在LMP 2/6- 31 G ** 和B3 LYP/6- 31 G ** 水平上的从头算和密度泛函计算表明，双环[4.2.0]辛烯异构体的热力学稳定性依次为：7-烯4a < 1（8）-烯4 b < 1-烯4c> 1（6）-烯4 e> 3-烯4f < 2-烯4d.提出了通过随后的β-氢化物消除和烯烃再插入异构化的机制。这些结果与1、2和7催化的双环[3.2.0]庚-6-烯（3a）的反应和Cp_2ZrCl_2/MAO（Cp = eta（5）-C_5H_5）催化的4a的反应形成对比，所有这些反应都以良好的产率（73-99%）产生聚合物。
In the presence of several Pd(II) catalysts, cis-bicyclo[4.2.0]oct-7-ene (4a) was found to undergo olefin isomerization ("ring walking") and oligomerization, resulting in the formation of cis-bicyclo[4.2.0]oct-2-ene (4d) and the low-molecular-mass cycloaliphatic oligomers 5a-d, respectively. The catalysts studied are [Pd(NCEt)(4)][BF4](2) (1), [(eta(3)-allyl)Pd(solv)(2)][SbF6] (2; solv = CH2Cl2), [(1,10-phenanthroline)Pd(CH3)(NC-(CH2)(6)CH3)][SbF6] (6), and [(2,9-dimethyl-1,10-phenanthroline)Pd(CH3)(NC(CH2)(6)CH3)][SbF6] (7). Isomerization included the formation of both 4d and the olefinic end groups of 5a-d and ranged from 94% using catalyst 7 to 29% employing catalyst 2. Ab initio and DFT calculations at the LMP2/6-31G** and B3LYP/6-31G** levels show that the thermodynamic stabilities of the bicydo[4.2.0]octene isomers increase in the order 7-ene 4a < 1(8)-ene 4b < 1-ene 4c approximate to 1(6)-ene 4e approximate to 3-ene 4f < 2-ene 4d. A mechanism of isomerization via subsequent beta-hydride eliminations and olefin reinsertions is proposed. These results are in contrast to the reactions of bicyclo[3.2.0]hept-6-ene (3a) catalyzed by 1, 2, and 7 and the reaction of 4a catalyzed by Cp2ZrCl2/MAO (Cp = eta(5)-C5H5), all of which produced polymers in good yields (73-99%).