N-杂环卡宾-铜络合物

Josephine Nakhla

在过去的20年中,关于N-杂环卡宾(NHC)配体的研究越来越受到关注。与所得络合物相关的电子效应和空间位阻效应相匹配,使得NHC成为设计作为催化剂的新型金属复合物的重要候选者。Nolan及其同事是使用NHC配体进行催化的先驱之一,他们报道了使用Cu-NHC进行各种催化转化的应用。α,β-不饱和酮和酯的共轭还原、酮的氢化硅烷化、末端烯烃的环丙烷化、烯化、卡宾转移反应、烯烃的氮杂环丙烷化和醛的亚甲基化(方案4)都是Cu-NHC复合物(特别是(IPr)CuCl)在现代催化手段中的一些实例。最后,这些催化剂具有空气和水分稳定性,可作为前体用于合成更多空气敏感复合物。1

N-杂环卡宾-铜络合物

方案 4.

Nolan及其同事描述了在PPh3、i-PrOH和TMSCHN2存在下,在醛(和酮)的烯化中使用了Cu-Imes卡宾复合物5。虽然有报道称使用Wilkinson催化剂可进行类似的烯化,但含Cu替代品提供了更经济的解决方案。官能团相容性非常好,因此能够形成官能化的脂肪族烯烃、二烯和苯乙烯,含有硝基(众所周知它对这类反应有害)、三氟甲基、氨基和酯官能团以及用吡啶取代的杂芳族烯烃、吡咯和吲哚衍生物(方案5)。在略微改变的反应条件下,异丙基衍生的卡宾复合物6也被证明在这类反应中非常有用(方案6)。2

吡啶、吡咯和吲哚衍生物

方案 5.

异丙基衍生的卡宾复合物

方案 6.

材料
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参考文献

1.
Díez-González S, Scott NM, Nolan SP. 2006. Cationic Copper(I) Complexes as Efficient Precatalysts for the Hydrosilylation of Carbonyl Compounds. Organometallics. 25(9):2355-2358. http://dx.doi.org/10.1021/om0600487
2.
Díez-González S, Nolan SP. 2008. Copper, Silver, and Gold Complexes in Hydrosilylation Reactions. Acc. Chem. Res.. 41(2):349-358. http://dx.doi.org/10.1021/ar7001655
3.
Jurkauskas V, Sadighi JP, Buchwald SL. 2003. Conjugate Reduction of ?,?-Unsaturated Carbonyl Compounds Catalyzed by a Copper Carbene Complex. Org.Lett.. 5(14):2417-2420. http://dx.doi.org/10.1021/ol034560p
4.
Lebel H, Davi M, Díez-González S, Nolan SP. 2007. Copper?Carbene Complexes as Catalysts in the Synthesis of Functionalized Styrenes and Aliphatic Alkenes. J. Org.Chem.. 72(1):144-149. http://dx.doi.org/10.1021/jo061781a
5.
Trost BM, Dong G. 2006. New Class of Nucleophiles for Palladium-Catalyzed Asymmetric Allylic Alkylation.Total Synthesis of Agelastatin A. J. Am. Chem. Soc.. 128(18):6054-6055. http://dx.doi.org/10.1021/ja061105q
6.
Fructos MR, Belderrain TR, Nicasio MC, Nolan SP, Kaur H, Díaz-Requejo MM, Pérez PJ. 2004. Complete Control of the Chemoselectivity in Catalytic Carbene Transfer Reactions from Ethyl Diazoacetate: AnN-Heterocyclic Carbene?Cu System That Suppresses Diazo Coupling. J. Am. Chem. Soc.. 126(35):10846-10847. http://dx.doi.org/10.1021/ja047284y
7.
Kaur H, Zinn FK, Stevens ED, Nolan SP. 2004. (NHC)CuI(NHC = N-Heterocyclic Carbene) Complexes as Efficient Catalysts for the Reduction of Carbonyl Compounds. Organometallics. 23(5):1157-1160. http://dx.doi.org/10.1021/om034285a
8.
Díez-González S, Nolan SP. 2008. N-heterocyclic carbene-copper complexes: Synthesis and applications in catalysis. [Internet]. Aldrichimica Acta2008, 41, 43..
9.
Lebel H, Davi M, Díez-González S, Nolan SP. 2007. Copper?Carbene Complexes as Catalysts in the Synthesis of Functionalized Styrenes and Aliphatic Alkenes. J. Org.Chem.. 72(1):144-149. http://dx.doi.org/10.1021/jo061781a