Catalytic in situ generation of Zn(II)-alkynilides under mild conditions:: A novel C=N addition process utilizing terminal acetylenes
Catalytic in situ generation of Zn(II)-alkynilides under mild conditions:: A novel C=N addition process utilizing terminal acetylenes
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DOI：
10.1021/ja993074n
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发表时间：
1999-12-08
影响因子：
15
通讯作者：
Carreira, EM
中科院分区：
文献类型：
--
作者：
Frantz, DE;Fässler, R;Carreira, EM
通过添加 CdO 或 CdN 形成 CC 键的新化学计量和催化反应的发现和研究对于持续开发有效的化学合成工艺至关重要。金属化末端炔烃是一类理想的多功能亲核试剂，可添加到各种亲电子试剂中，提供具有良好合成多功能性的加合物。 1, 2 通常用于此类方法的炔苯胺通常由乙炔和有机锂（即BuLi） 3 或有机镁碱（即EtMgBr）制备。 4 由于所用的醛和亚胺与此类碱性试剂和亲核试剂不相容，因此炔烃去质子化必须作为单独的步骤进行。 5 在不使用如此强的自燃化学计量碱的情况下，将炔烃亲核加成到 CdO 或 CdN 上的能力将大大简化该过程。 6 更重要的是，在与亲电子反应伙伴兼容的条件下，从相应的末端炔原位催化生成反应性过渡金属炔苯胺，将为开发导致 CC 键形成的新的、有效的不对称过程提供新的途径。在这篇文章中，我们记录了我们的观察结果，涉及在催化过渡金属和碱、10 mol% Zn (OTf) 2 与 25 mol% iPr2NEt (eq 1) 的结合下，在温和条件 (23 C) 下，将末端炔烃加成到硝酮上。据观察，该反应适用于 N-苄基硝酮和多种末端乙炔，包括烯炔、三甲基甲硅烷基乙炔、炔丙基三甲基硅烷以及炔丙基溴。
The discovery and study of new stoichiometric and catalytic reactions that lead to CC bond formation by additions to CdO or CdN are of fundamental importance in the continuing development of efficient processes for chemical synthesis. Metalated terminal alkynes are an ideal class of versatile nucleophiles that add to a wide range of electrophiles, affording adducts of great synthetic versatility. 1, 2 The alkynilides typically employed in such processes are commonly prepared from an acetylene and organolithium (ie, BuLi) 3 or organomagnesium bases (ie, EtMgBr). 4 Because the aldehydes and imines used are incompatible with such basic and nucleophilic reagents, alkyne deprotonation must necessarily be carried out as a separate step. 5 The ability to carry out nucleophilic additions of alkynes to CdO or CdN without the use of such strong, pyrophoric, stoichiometric bases would lead to great simplification of the processes. 6 Of greater importance, the catalytic generation of reactive transitionmetal alkynilides from the corresponding terminal alkyne in situ under conditions that are compatible with electrophilic reaction partners would provide fresh avenues for the development of new, efficient asymmetric processes leading to CC bond-formation. In this contribution, we document our observations involving the addition of terminal alkynes to nitrones in the presence of both catalytic transition-metal and base, 10 mol% Zn (OTf) 2 in combination with 25 mol% iPr2NEt (eq 1), under mild conditions (23 C). The reaction is observed to work well with N-benzyl nitrones and a broad range of terminal acetylenes including enynes, trimethylsilyl acetylene, propargyl trimethylsilane, as well as propargyl bromide.