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Formation of para-quinomethanes via 4-aminobutylcatechol oxidation and ortho-quinone tautomerism

机译:通过4-氨基丁基邻苯二酚氧化和邻醌互变异构形成对喹啉甲烷

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摘要

Enzymatic and chemical oxidation of 4-(4-N,N-dialkylaminobutyl)catechols leads to formation of 1,1-dialkyl-pyrrolidinium salts in good yield. It is proposed that these products are formed by tautomerism of the initially formed ortho-quinones to para-quinomethanes. The corresponding secondary amines do not form para-quino-melhanes but cyclise giving tetrahydro-1H-benzo[b]azepine-7,8-diones. The failure of the dialkylaminobutyl derivatives to cyclise to bicyclic betaines, in a manner analogous to lower homologues and monoalkylaminobutyl derivatives, is attributed to steric hindrance. This proposal is supported by evidence that the sterically hindered N-tert-butylaminobutyl derivative, in contrast to other secondary amines, does not cyclise but gives a para-quinomethane-derived product. Based on pulse radiolysis and spectrophotometric evidence, para-quinomethane formation appears to be much slower than cyclisation and only occurs when cyclisation is unfavourable. The ortho-quinones formed from 5-aminopentylcatechols neither cyclise nor tautomerise suggesting that the chain length in these derivatives is too long for both cyclisation and intramolecular deprotonation.
机译:4-(4-N,N-二烷基氨基丁基)邻苯二酚的酶促和化学氧化导致高产率形成1,1-二烷基-吡咯烷鎓盐。提出这些产物是由最初形成的邻醌到对喹啉甲烷的互变异构形成的。相应的仲胺不形成对喹啉-蜜胺,而是环化生成四氢-1H-苯并[b]氮杂-7,8-二酮。二烷基氨基丁基衍生物不能以类似于低级同源物和单烷基氨基丁基衍生物的方式环化成双环甜菜碱,这归因于位阻。该提议得到以下证据的支持:与其他仲胺相比,空间受阻的N-叔丁基氨基丁基衍生物不会环化,但会产生对喹啉甲烷衍生的产物。根据脉冲辐射分解和分光光度法的证据,对喹啉甲烷的形成似乎比环化慢得多,并且仅在环化不利时才会发生。由5-氨基戊基邻苯二酚形成的邻醌既不环化也不互变异构,这表明这些衍生物的链长对于环化和分子内去质子化而言都太长。

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