Rivero Alexandra R, Fernández Israel, Sierra Miguel A
Departamento de Química Orgánica, Facultad de Química, Universidad Complutense, 28040 Madrid (Spain), Fax: (+34) 913944310.
Chemistry. 2014 Jan 27;20(5):1359-66. doi: 10.1002/chem.201302029. Epub 2013 Dec 16.
The [5+2] and [6+2] cycloaddition reactions of vinylaziridines and vinylazetidines with ketenes generated photochemically from chromium(0) and molybdenum(0) Fischer carbene complexes have been investigated. These processes constitute a straightforward and efficient route to azepanones and azocinones, respectively. The peculiar electronic properties of the metalated ketenes allow for the introduction of electron-rich substituents in the final cycloadducts, a difficult task using conventional organic chemistry procedures. The versatility of the process is demonstrated by using Cr(0) Fischer bis(carbene) complexes as metalated bis(ketene) precursors. These species produce tethered bis(azepanone)s in a single step under mild reaction conditions. Density functional theory calculations point to a stepwise reaction pathway through the initial nucleophilic attack of the nitrogen atom of the aziridine on the metalated ketene, followed by ring closure of the zwitterionic intermediate formed.
研究了乙烯基氮丙啶和乙烯基氮杂环丁烷与由铬（0）和钼（0）费歇尔卡宾配合物光化学产生的烯酮的[5 + 2]和[6 + 2]环加成反应。这些过程分别构成了直接且高效地合成氮杂环庚烷酮和氮杂环辛烷酮的途径。金属化烯酮独特的电子性质使得在最终环加成产物中能够引入富电子取代基，而这用传统有机化学方法是一项艰巨的任务。通过使用铬（0）费歇尔双（卡宾）配合物作为金属化双（烯酮）前体，证明了该过程的多功能性。这些物质在温和的反应条件下通过一步反应生成了连接的双（氮杂环庚烷酮）。密度泛函理论计算表明反应途径是分步的，首先是氮丙啶的氮原子对金属化烯酮进行亲核进攻，随后形成的两性离子中间体闭环。
