Carbonyl imines from oxaziridines: generation and cycloaddition of N-O=C dipoles.
Carbonyl imines from oxaziridines: generation and cycloaddition of N-O=C dipoles.
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来自氧氮丙啶的羰基亚胺：N-O=C 偶极子的生成和环加成。
DOI：
10.1002/anie.200905801
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Yoon,TehshikP
中科院分区：
文献类型：
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作者：
Partridge,KatherineM;Guzei,IliaA;Yoon,TehshikP
硝酮、叠氮化合物和相关的1，3-偶极化合物的环加成反应在有机合成、化学生物学和材料科学中具有重要的应用价值。支持我们理解这一广泛类别反应的概念模型首先由Huisgen于1963年正式化。这一对有机化学的开创性贡献为化学家提供了一个统一的框架来理解1，3-偶极化合物的结构和反应性，并预测了当时未知的几种基本1，3-偶极的结构。随后的研究已经确定了许多这些预测的1，3-偶极物种的环加成反应。v然而，羰基亚胺（例如，3，方案1）在Huisgen最初预测的半个世纪中仍然难以捉摸。虽然这些不寻常的偶极已被假定为硝基芳烃的光化学分解的中间体，vi没有化合物产生的偶极环加成羰基亚胺先前已被报道。在这篇文章中，我们证明了羰基亚胺可以有效地通过刘易斯酸催化重排的N-磺酰基oxaziridines和捕获通过环加成与各种偶极亲。我们最近报道，TiCl 4催化重排的N-磺酰基oxaziridinesvii（“戴维斯oxaziridines”，例如，1）产生一类新的缺电子N-磺酰基硝酮（2）。viii这些高度不稳定的硝酮可以通过与各种苯乙烯烯烃的环加成反应有效地原位拦截，从而提供具有非常高水平的顺式选择性的1，2-异恶唑烷（5，表1，条目1）。在探索这种新反应性的研究过程中，我们令人惊讶地观察到，多种其它刘易斯酸催化剂（条目2-5）产生我们鉴定为区域异构体和非对映异构体1，2-异恶唑烷4的副产物。ix 4的产生表明1的刘易斯酸催化重排可以生成N-磺酰基硝酮或N-磺酰基羰基亚胺，并且这两个1，3-偶极之间的分配可以通过催化剂的特性来控制。被这一观察所吸引，我们开始了一项研究，以开发将导致羰基亚胺环加合物4的排他性形成的条件，这将使我们能够更详细地探索这种反应性。
Cycloaddition reactions of nitrones, i azides, ii and related 1, 3-dipolar species iii have become recognized as powerful tools for the construction of compounds with great utility in organic synthesis, chemical biology, and materials science. The conceptual model that underpins our understanding of this broad class of reactions was first formalized by Huisgen in 1963. iv This seminal contribution to organic chemistry provided chemists with a unified framework for understanding the structure and reactivity of 1, 3-dipolar compounds, and also predicted the structures of several elementary 1, 3-dipoles that were unknown at the time. Subsequent research has identified cycloaddition reactions of many of these predicted 1, 3-dipolar species. v However, carbonyl imines (eg, 3, Scheme 1) have remained elusive in the halfcentury since Huisgen’s initial prediction. Although these unusual dipoles have been postulated to be intermediates in the photochemical decomposition of nitroarenes, vi no compounds resulting from dipolar cycloadditions of carbonyl imines have previously been reported. In this communication, we demonstrate that carbonyl imines can be efficiently generated by Lewis acid-catalyzed rearrangement of N-sulfonyl oxaziridines and trapped by cycloaddition with a variety of dipolarophiles.We recently reported that TiCl4-catalyzed rearrangement of N-sulfonyl oxaziridinesvii (“Davis oxaziridines”, eg, 1) produces a new class of electron-deficient N-sulfonyl nitrones (2). viii These highly unstable nitrones can be efficiently intercepted in situ by cycloaddition with a variety of styrenic olefins, affording 1, 2-isoxazolidines with very high levels of cis selectivity (5, Table 1, entry 1). In the course of investigations probing this novel reactivity, we made the surprising observation that a variety of other Lewis acid catalysts (entries 2–5) produce a side product that we identified as the regioisomeric and diastereomeric 1, 2-isoxazolidine 4. ix The production of 4 suggested that Lewis acid-catalyzed rearrangement of 1 could generate either N-sulfonyl nitrones or N-sulfonyl carbonyl imines, and that the partitioning between these two 1, 3-dipoles could be controlled by the identity of the catalyst. Intrigued by this observation, we initiated an investigation to develop conditions that would result in exclusive formation of carbonyl imine cycloadduct 4, which would enable us to explore this reactivity in greater detail.