Photochemical rearrangements of quinone monoketals
Photochemical rearrangements of quinone monoketals
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DOI：
10.1016/0040-4020(96)00207-4
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发表时间：
1996-04-15
期刊：
影响因子：
2.1
通讯作者：
Nunn, DS
中科院分区：
文献类型：
--
作者：
Pirrung, MC;Nunn, DS
我们研究了15种以上醌环单缩酮的光化学，它们是由二甲基缩酮经二醇交换、Swenton氧化/水解或直接缩酮化制得的。它们在酸性介质中的反应通常由环己二烯酮光化学（二-π-甲烷）重排的经典机制来解释：光环化成质子化的环丙烷-氧烯丙基阳离子，然后溶剂分解。该反应途径在水解后提供β-羧基取代的环戊烯酮。在醌单缩酮的β-位具有取代基的情况下，重排选择性适度地有利于更多取代的烯烃产物。在醌单缩酮的α-位具有取代基的情况下，重排选择性强烈地有利于较少取代的烯烃产物。可能的机械推理来解释这些意见。(C)1996年Elsevier Science Ltd.
We have studied the photochemistry of over 15 quinone cyclic monoketals, which were prepared by diol exchange from the dimethyl ketals, Swenton oxidation/hydrolysis, or direct ketalization. Their reactions in acidic media are generally explained by the classical mechanism for cyclohexadienone photochemical (di-pi-methane) rearrangements: photocyclization to a cyclopropane-oxyallylcation that is protonated, followed by solvolysis. This reaction pathway provides, after hydrolysis, beta-carboxy-substituted cyclopentenones. With a substituent at the beta-position of the quinone monoketal, rearrangement selectivity is modestly in favor of the more substituted alkene product. With a substituent at the alpha-position of the quinone monoketal, rearrangement selectivity is strongly in favor of the less substituted alkene product. Possible mechanistic reasoning to explain these observations is offered. (C) 1996 Elsevier Science Ltd.