REGIOSPECIFIC ADDITION OF MONOOXYGENATED DIENES TO HALO QUINONES
REGIOSPECIFIC ADDITION OF MONOOXYGENATED DIENES TO HALO QUINONES
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DOI：
10.1021/jo00252a031
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发表时间：
1988-08-19
影响因子：
3.6
通讯作者：
BRASSARD, P
中科院分区：
文献类型：
--
作者：
BOISVERT, L;BRASSARD, P
尽管它们相对于先前研究的富电子类似物的极性降低，但单氧二烯也与卤代醌反应区域特异性。相应的加合物可以很容易地在硅胶上芳构化为结构明确的异构多取代萘醌，因此为随后的区域特异性成环提供了方便的底物。这种方法的范围说明了几种天然产物的有利合成：chimaphilin，6-methylalizarin，6-methylxanthopurpurin，和barleriaquinone。加合物还可以产生一系列产物，其中二烯的氧官能团作为羟基保留在醌中。在此基础上，1-氧代二烯和卤代醌的加合物可被Jones试剂有效氧化，而2-氧代二烯和卤代醌的加合物对二氧化锰的反应更好。加合物中取代基的相对位置很容易通过比较一些羟基化的氧化产物与结构明确的已知化合物来确认。该方法再次通过包括白花丹素、soranjidiol、异大黄酚及其8-甲基醚和isozyganein及其5-甲基醚的许多天然产物的快速合成来说明。
In spite of their decreased polarity with respect to previously studied electron-rich analogues, monooxygenated dienes also react regiospecifically with halo quiñones. The corresponding adducts can easily be aromatized on silica gel to isomeric polysubstituted naphthoquinones of unambiguousstructure and therefore provide ready access to substrates for subsequent regiospecific annulations. The scope of this approach is illustrated by advantageous syntheses of several natural products: chimaphilin, 6-methylalizarin, 6-methylxanthopurpurin, and barleriaquinone. The adducts can also give rise to a series of products in which theoxygen function of the dienes is preserved as a hydroxyl group in the quinone. To this end adducts derived from 1-oxygenated dienes and halo quiñones were oxidized effectively with Jones’ reagent while those obtainedfrom the 2-oxygenatedisomers responded better to manganese dioxide. Relative positions of substituents in the adducts were readily confirmed by comparison of some of the hydroxylated oxidation products with known compounds of unambiguousstructure. The method is again illustrated by the ready synthesis of a number of natural products including plumbagin, soranjidiol, isochrysophanol and its 8-methyl ether, and isozyganein and its 5-methyl ether.