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首页> 外文期刊>Chemistry: A European journal >Single-step microwave-mediated synthesis of oxazoles and thiazoles from 3-oxetanone: A synthetic and computational study
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Single-step microwave-mediated synthesis of oxazoles and thiazoles from 3-oxetanone: A synthetic and computational study

机译：微波一步法从3-氧杂环丁酮合成恶唑和噻唑的合成和计算研究

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The direct microwave-mediated condensation between 3-oxetanone and primary amides and thioamides has delivered moderate to good yields of (hydroxymethyl)oxazoles and (hydroxymethyl)thiazoles. The reactions use a sustainable solvent and only require short reaction times. These are highly competitive methods for the construction of two classes of valuable heteroarenes, which bear a useful locus for further elaboration. Electronic structure calculations have shown that the order of events involves chalcogen atom attack at sp~3 carbon and alkyl-oxygen cleavage. The critical role of acid catalysis was shown clearly, and the importance of acid strength was demonstrated. The calculated barriers were also fully consistent with the observed order of thioamide and amide reactivity. Spontaneous ring opening involves a modest degree of C-O cleavage, moderating the extent of strain relief. On the acid-catalysed pathway, C-O cleavage is less extensive still, but proton transfer to the nucleofuge is well advanced with the carboxylic acid catalysts, and essentially complete with methanesulfonic acid. Open sesame: The direct microwave-mediated condensation between 3-oxetanone and primary amides and thioamides has delivered moderate to good yields of oxazoles and thiazoles. The reactions use a sustainable solvent, require only short reaction times and represent a highly competitive method for the construction of two classes of valuable heteroarenes. Electronic structure calculations have been used to probe a range of potential reaction mechanisms (see figure).
机译：3-氧杂环丁酮与伯酰胺和硫代酰胺之间的直接微波介导的缩合反应已产生中等至良好收率的（羟甲基）恶唑和（羟甲基）噻唑。反应使用可持续的溶剂，只需要很短的反应时间。这些是构建两类有价值的杂芳烃的高度竞争方法，它们具有进一步加工的有用位置。电子结构计算表明，事件的顺序涉及硫原子在sp〜3碳原子上的进攻以及烷基-氧的裂解。清楚地表明了酸催化的关键作用，并证明了酸强度的重要性。计算的势垒也与所观察到的硫酰胺和酰胺反应性顺序完全一致。自发的开环涉及适度的C-O裂解，减缓了应变释放的程度。在酸催化的途径上，C-O裂解仍然不太广泛，但是使用羧酸催化剂可以很好地促进质子转移到核反应堆中，并且基本上可以用甲磺酸完成。开放式芝麻：3-氧杂环丁酮与伯酰胺和硫代酰胺之间直接的微波介导缩合反应已产生中等至良好收率的恶唑和噻唑。反应使用可持续的溶剂，仅需要短的反应时间，就代表了建设两类有价值的杂芳烃的高度竞争方法。电子结构计算已用于探究一系列潜在的反应机理（见图）。

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