Palladium- and cobalt-mediated cyclisations of halo-polyenes: A comparative study
Palladium- and cobalt-mediated cyclisations of halo-polyenes: A comparative study
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DOI：
10.1039/p19960001081
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发表时间：
1996-06-07
期刊：
影响因子：
--
通讯作者：
Kam, TS
中科院分区：
文献类型：
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作者：
Ali, A;Gill, GB;Kam, TS
钴（I）介导的单环和双环的卤代多烯进行了比较，并与相应的反应使用赫克反应。在所研究的案例中，发现这些程序相互补充，各有优缺点。因此，在Heck条件下处理乙烯基碘1以93%的产率得到新的1，3-二烯3，而1与钴（I）salophen之间的反应导致形成黑色晶体形式的有机钴络合物4（类似于50%）。随后照射4，以85%的产率得到6，5-环稠合双环5。以类似的方式，与类似的乙烯基碘8的Heck反应产生6-环环化的产物9，随后是β-氢化物消除，而与8的相应的钴介导的反应产生新的有机钴10，尽管产率仅为低（类似于20%）。在类似于Overman等人研究的反应中，与二烯基芳基碘14的Heck反应显示导致双环16和三环17以1：1比率的混合物。相比之下，用钴（I）salophen处理14主要产生四氢萘18。碘代二烯33在Heck反应条件下生成螺环35，相关的螺环42使用钴（I）介导的反应由溴代缩醛40经41产生。
Cobalt(I)-mediated mono- and bi-cyclisations of halo-polyenes are compared and contrasted with corresponding reactions using the Heck reaction. The procedures are found to complement one another, with each having advantages and disadvantages, in the cases studied. Thus, treatment of the vinyl iodide 1 under Heck conditions led to the novel 1,3-diene 3 in 93% yield, whereas reaction between 1 and cobalt(I) salophen resulted in the formation of the organocobalt complex 4 (similar to 50%) as black crystals. Subsequent irradiation of 4 then led to the 6,5-ring fused bicycle 5 in 85% yield. In similar fashion, a Heck reaction with the analogous vinyl iodide 8 produced the product 9 of 6-ring cyclisation followed by beta-hydride elimination, whereas the corresponding cobalt-mediated reaction with 8 led to the new organocobalt 10 albeit in only low yield (similar to 20%). In reactions akin to those studied by Overman et al., Heck reaction with the dienyl aryl iodide 14 was shown to lead to a mixture of the bicycle 16 and the tricycle 17 in a 1:1 ratio. By contrast treatment of 14 with cobalt(I) salophen produced largely the tetralin 18. The iodo-diene 33 gave rise to the spirocycle 35 under Heck reaction conditions, and the related spirocycle 42 was produced from the bromo-acetal 40 via 41, using cobalt(I) mediated reactions.