The syntheses and properties of the cycloadducts of p-benzoquinones with 1,3-dipoes

1.芳香腈氧化物与2,5-和2,6-二烷基对苯醌的一些1,3-偶极环加合物发生碱诱导异构化。根据光谱数据，我们提出了异构化产物的结构为开环再循环形成的异恶唑-融合衍生物。然而，2,5-二叔丁基-对苯醌（25DBQ）与2,6-二氯苯腈氧化物（CNO）异构化产物的x射线结构测定表明，其中一个叔丁基从桥头堡位置迁移到邻近的羰基碳原子上。在桥头堡位置有甲基的环加合物没有发生异构化。我们详细研究了重排的机制。我们还研究了一些新的1,3-偶极环加合物与碱的反应。25DBQ与n -苯基- α -对硝基苯基硝基硝酮的环加合物与碱反应无异构产物。25DBQ与三甲基硅基重偶氮的反应生成了吡唑啉衍生物，而不是简单的1,3-偶极环加合物。该化合物与氢氧化钠反应，随着桥头堡叔丁基的迁移，异构化成吡唑衍生物。同样在2-对丁基萘醌与CNO的环加合物中，桥头堡正丁基转移到邻近的羰基碳上形成异恶唑衍生物。看来，这种极不寻常的烷基迁移是由环加合物的杂环部分芳构化引起的。用乙酸酐-硫酸处理环加合物，消除了桥头堡t-Bugroup，得到异恶唑-二乙酸对苯二酚衍生物。重排产物也容易发生类似的乙酰化反应，但最终产物是异恶唑融合的儿茶酚衍生物和/或对苯二酚二乙酸酯衍生物。2-叔丁基-5-甲基-对苯醌与大量过量的氧化腈反应得到1:3环加合物，而不是1:2环加合物。环加成发生在两个C=C键和一个C=O键上。三甲基乙烷与对苯醌的环加成在C=C键上得到1:1环加合物。其他的烷基取代苯醌也得到相应的环加合物。少

1.Some of the 1,3-dipolar cycloadducts of aromatic nitrile oxides with 2,5- and 2,6-dialkyl-p-benzoquinones undrgo base-induced isomerization. We have proposed the structure of the isomerized products as isoxazole-fused derivatives which were formed by ring-opening and recyclization with a base from spectroscopic data. However the X-ray structure determination of the isomerized product from 2,5-di-tert-butyl-p-benzoquinone (25DBQ) with 2,6-dichlorobenzonitrile oxide (CNO) showed that one of the tert-butyl group migrated from the bridgehead poositon to neighboring carbonyl carbon atom. The cycloadducts which have a methyl group at the bridgehead position did not undergo isomerization. We investigate the mechanism of rearrangement in detail.Also we investigate the reaction of some novel 1,3-dipolar cycloadducts with base. The cycloadduct of 25DBQ with N-phenyl-alpha-p-nitrophenylnitrone yields no isomerized product by the reaction with base. The reaction of 25DBQ with trimethylsilyldiazo … More methane generates pyrazoline derivative instead of simple 1,3-dipolar cycloadduct. This compound reacts with NaOH and isomerize to pyrazole derivative with the migration of the bridgehead tert-butylgroup. Also in the case of the cycloadduct of 2-tet-butylnaphthoquinone with CNO,the bridgehead trt-butyl group moves to neighboring carbonyl carbon to form isoxazole derivative. It is seemed that such a very unusual alkylmigration results from the aromatization of heterocyclic moieties of cycloadducts.2.Treatment of the cycloadducts with acetic anhydride-sulkfuric acid caused elimination of the bridgehead t-Bugroup to afford the isoxazole-fused hydroquinone diacetate derivatives. The rearranged products were also susceptible to the similar acetylation, but the resulting products were isoxazole-fused catechol derivatives and/or hydroquinone diacetate derivatives.3.The reaction of 2-tert-butyl-5-methyl-p-benzoquinone with a large excess of the nitrile oxide gave the 1 : 3 cycloadduct instead of the 1 : 2 cycloadduct. The cycloaddition occurred at two C=C bonds and one C=O bond.4.The cycloaddition of trimethylenemethane with p-benzoquinones gave the 1 : 1 cycloadduct at the C=C bond. The other alkyl-substituted benzoquinones also gave the corresponding cycloadducts. Less