Transfer semihydrogenation of alkynes catalyzed by a zero-valent palladium N-heterocyclic carbene complex
Transfer semihydrogenation of alkynes catalyzed by a zero-valent palladium N-heterocyclic carbene complex
复制标题
DOI：
10.1002/anie.200705638
复制
发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Elsevier, Cornelis J.
中科院分区：
文献类型：
--
作者：
Hauwert, Peter;Maestri, Giovanni;Elsevier, Cornelis J.
催化转移氢化是一种温和而有效的还原羰基官能团的方法，其涉及醇或甲酸铵作为氢供体和RuII、IrI或RhI络合物作为催化剂。[1，2]酮和亚胺的转移氢化是众所周知的，因为这些极性双键容易还原成相应的醇和胺，[3-5]而非极性碳-碳多重键的转移氢化更困难。[2a因此，尽管已知几种均相催化体系用于烯烃的转移氢化，但仅报道了一种用于将炔转移半氢化成烯烃的均相催化体系（方案1）。该方法对芳族炔没有化学选择性，产物烯烃可以进一步氢化成相应的烷烃。此外，催化剂含有大量的亲氧膦配体。[7]芳族炔在其它反应中也被证明是困难的底物，特别是转移氢化和使用二氢的氢化。[8]传统上，炔的半氢化是用林德拉催化剂和氢气进行的。该系统将炔烃还原为Z烯烃，但需要精心设计的实验装置和对氢吸收的严格监测，以防止过度还原为烷烃。除了这些实际上的不便之外，
Catalytic transfer hydrogenation is a mild and effective way of reducing carbonyl functionalities that involves alcohols or ammonium formate as hydrogen donors and RuII, IrI, or RhI complexes as catalysts.[1, 2] Transfer hydrogenation of ketones and imines is well known since these polar double bonds are easily reduced to the corresponding alcohols and amines,[3–5] whereas transfer hydrogenation of non-polarized carbon–carbon multiple bonds is more difficult.[2a, 5–7] Thus, although several homogeneous catalytic systems are known for the transfer hydrogenation of alkenes, only one has been reported for the transfer semihydrogenation of alkynes to alkenes (Scheme 1). This procedure is not chemoselective for aromatic alkynes, and the product alkene can be further hydrogenated to the corresponding alkane. Furthermore, the catalyst contains large amounts of oxophilic phosphine ligand.[7] Aromatic alkynes have also proven to be difficult substrates in other reactions, particularly transfer hydrogenation and hydrogenation using dihydrogen.[8] The semihydrogenation of alkynes is traditionally performed with Lindlar s catalyst and dihydrogen. This system reduces alkynes to Z alkenes but requires an elaborate experimental setup and strict monitoring of the hydrogen uptake to prevent over-reduction to the alkane. Apart from these practical inconveniences, partial isomerization of the