(3,5-Di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)acetic acid 1a underwent on heating a new cyclodimerization reaction affording a 1 : 1 mixture of the racemic cis- and trans-isomeric lactone-acids 2. The decisive structure elucidation of 2 was carried out after its mild esterification with diazomethane and separation of the racemic isomeric methyl esters 3a and 3b. The attempted esterification of 2 with methanol and sulfuric acid gave only the methyl diarylacetate 4. In contrast to 1a, which contains the carboxylic acid functionality no cyclodimerization was observed with the corresponding methyl ester 1b or nitrile 1c.
(3,5-二-tert-丁基-4-氧代环己-2,5-二烯基)
乙酸1a在加热时发生了新的环二聚反应,生成了
cis-和
trans-异构的内酯酸
2的1:1混合物。通过与
重氮甲烷的轻微酯化和分离得到了外消旋异构的甲酯
3a和
3b,对
2的关键结构阐明是在此之后进行的。尝试用
甲醇和
硫酸酯化
2只得到了甲基二
苯乙酸酯
4。与含有
羧酸官能团的
1a不同,相应的甲酯
1b或腈
1c没有观察到环二聚反应。