Efficient Synthesis and Subsequent Transformations of Phenylsulfanylbicyclo[2.2.2]octenones and Phenylselenylbicyclo[2.2.2]octenones
Efficient Synthesis and Subsequent Transformations of Phenylsulfanylbicyclo[2.2.2]octenones and Phenylselenylbicyclo[2.2.2]octenones
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DOI：
10.1021/jo802295p
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发表时间：
2009-02-20
影响因子：
3.6
通讯作者：
Liao, Chun-Chen
中科院分区：
文献类型：
--
作者：
Gao, Shih-Yu;Chittimalla, Santhosh Kumar;Liao, Chun-Chen
掩蔽的邻苯醌2与苯基乙烯基硫醚和苯基乙烯基硒醚的反电子需求Diels-Alder反应分别以优异的区域选择性和立体选择性提供了高度官能化的双环[2.2.2]辛烯酮衍生物3和4，产率高达90%。对具有硫官能团的双环[2.2.2]辛烯酮衍生物3进行氧化-消除过程，以良好的产率得到双环[2.2.2]辛二烯酮体系7。在还原过程中，Diels-Alder加合物3e和4 e生成8，而由其他加合物3a-d和4a-d生成的碳中心自由基根据取代模式和所用试剂（Raney-Ni或n-Bu 3SnH）提供各种重排产物9-13。令人惊讶的是，这些自由基表现出优先的羰基官能团的烯双键，导致有趣的重排反应的机械重要性和可能的合成效用。有趣的是，由Diels-Alder加合物3a-d还原得到的醇顺利地进行脱硫，以高产率得到脱硫产物;因此，“还原-脱硫-氧化”的迂回方法提供了一个不重排的脱硫双环[2.2.2]辛烯酮的入口。
Inverse-electron-demand Diels-Alder reactions of masked o-benzoquinones 2 with phenyl vinyl sulfide and phenyl vinyl selenide furnished highly functionalized bicyclo[2.2.2]octenone derivatives 3 and 4, respectively, in excellent regio- and stereoselectivities and yields up to 90%. The bicyclo[2.2.2]octenone derivatives 3 with the sulfur functionality were subjected to an oxidation-elimination process to furnish bicyclo[2.2.2]octadienone systems 7 in good yields. During the reduction process, the Diels-Alder adducts 3e and 4e led to 8, whereas the carbon-centered radicals generated from the other adducts 3a-d and 4a-d provided various rearranged products 9-13 depending on the substitution pattern and reagents utilized (Raney-Ni or n-Bu3SnH). Surprisingly these radicals showed preference for the carbonyl functionality to the olefinic double bond, leading to interesting rearrangement reactions of mechanistic importance and possible synthetic utility. Interestingly the alcohols obtained from the reduction of Diels-Alder adducts 3a-d underwent desulfurization smoothly to give desulfurized products in high yields; thus a detoured method of "reduction-desulfurization-oxidation" provides an entry to desulfurized bicyclo[2.2.2]octenones without rearrangement.