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首页> 外文期刊>Chemistry: A European journal >Understanding the nature of the molecular mechanisms associated with the competitive Lewis acid catalyzed [4+2] and [4+3] cycloadditions between arylidenoxazolone systems and cyclopentadiene: A DFT analysis
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Understanding the nature of the molecular mechanisms associated with the competitive Lewis acid catalyzed [4+2] and [4+3] cycloadditions between arylidenoxazolone systems and cyclopentadiene: A DFT analysis

机译：了解与竞争性路易斯酸催化的芳基异恶唑酮系统和环戊二烯之间的[4 + 2]和[4 + 3]环加成反应相关的分子机制的性质：DFT分析

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摘要

The molecular mechanisms of the reactions between aryliden-5(4H)-oxazolone 1, and cyclopentadiene (Cp), in presence of Lewis acid (LA) catalyst to obtain the corresponding [4+2] and [4+3] cycloadducts are examined through density functional theory (DFT) calculations at the B3LYP/6-31G* level. The activation effect of LA catalyst can be reached by two ways, that is, interaction of LA either with carbonyl or carboxyl oxygen atoms of 1 to render [4+2] or [4+3] cycloadducts. The endo and exo [4+2] cycloadducts are formed through first reaction is a stepwise [4+3] cyclo-adducts are formed through a highly asynchronous concerted mechanism associated to a Michael-type addition of Cp to the beta-conjugated position of alpha,beta-unsaturated carbonyl framework of 1. Coordination of LA catalyst to the carboxyl oxygen yields a highly functionalized compound, 3, through a domino reaction. For this process, the del-Crafts-type addition of the electrophilically activated carbonyl group of 1 to Cp and subsequent cyclization of the corresponding zwitterionic intermediate to yield the corresponding [4+3] cycloadduct. The next rearrangement is the nucleophilic trapping of this cycloadduct by a second molecule of Cp to yield the final adduct 3. A new reaction pathway for the [4+3] cycloadditions emerges from the present study.
机译：研究了路易斯酸（LA）催化剂存在下aryliden-5（4H）-恶唑酮1与环戊二烯（Cp）之间反应的分子机理，以获得相应的[4 + 2]和[4 + 3]环加合物通过密度泛函理论（DFT）在B3LYP / 6-31G *水平上进行计算。 LA催化剂的活化作用可以通过两种方式达到，即LA与1的羰基或羧基氧原子相互作用以产生[4 + 2]或[4 + 3]环加合物。内和外[4 + 2]环加合物是通过第一个反应形成的;逐步的[4 + 3]环加合物是通过高度异步协同的机理形成的，该机理与Cp的迈克尔型加成到β-共轭位置有关α，β，β-不饱和羰基骨架1.通过多米诺反应将LA催化剂配位到羧基氧上生成高度官能化的化合物3。对于该方法，将1的亲电子活化的羰基的del-Crafts型加到Cp上，然后将相应的两性离子中间体环化，得到相应的[4 + 3]环加合物。下一个重排是通过第二个Cp分子对该环加合物的亲核捕获，以产生最终的加合物3。本研究提出了[4 + 3]环加成的新反应途径。

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