Homogeneous catalytic hydroamination of alkynes and allenes with ammonia
Homogeneous catalytic hydroamination of alkynes and allenes with ammonia
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DOI：
10.1002/anie.200801136
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Bertrand, Guy
中科院分区：
文献类型：
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作者：
Lavallo, Vincent;Frey, Guido D.;Bertrand, Guy
氮-碳键普遍存在于从化工原料到制药的各种产品中。由于氨是产量最大、成本最低的大宗化学品之一，合成化学的最大挑战之一是开发原子高效的工艺，将NH3与简单的有机分子结合起来，形成氮碳键。过渡金属配合物可以很容易地使各种N-H键具有足够的活性来进行官能化，包括伯胺和仲胺的N-H键。然而，除了少数例外，[1，2]金属与氨反应生成所谓的惰性Lewis酸碱络合物，这是Werner在19世纪末首次认识到的。因此，NH3的均相催化官能化一直难以捉摸[4]，直到最近沈和Hartwig[5]以及Surry和Buchwald[6]在化学计量比碱的存在下发现了钯催化的芳基卤化物与氨的偶联反应。一种更吸引人的方法是将NH3加到碳-碳多键上，该过程理想地以100%原子经济性发生。尽管各种均相催化剂，包括碱金属、早期[9]和晚期过渡金属、[10]、d-[11]和f-块元素[12]已被用于实现所谓的氢胺化反应，在此，我们报道了由环烷基(氨基)卡宾(CAAc)[14]配体支撑的阳离子金(I)配合物很容易催化各种未活化的炔烃和烯烃的氨加成反应，从而提供了一系列不同的线性和环状含氮化合物。我们最近表明，阳离子CAAc-金配合物A非常健壮，对炔烃表现出不寻常的催化反应活性。[15]这一发现促使我们研究这种络合物是否能够充分激活炔烃以实现NH3的加成。过量的氨被冷凝到一个可密封的核磁共振管中，其中含有A(5mol%)、3-己炔和重氢苯。当加热到160℃，3.5小时，干净的NH3添加得到伯亚胺2a，相应的烯胺的预期互变异构体(表1)。
Nitrogen–carbon bonds are ubiquitous in products ranging from chemical feedstock to pharmaceuticals. As ammonia is among the least expensive bulk chemicals produced in the largest volume, one of the greatest challenges of synthetic chemistry is to develop atomefficient processes for the combination of NH3 with simple organic molecules to create nitrogen–carbon bonds. Transition-metal complexes can readily render a variety of N–H bonds reactive enough to undergo functionalization, including those of primary and secondary amines. However, with a few exceptions,[1, 2] metals react with ammonia to afford supposedly inert Lewis acid–base complexes, as first recognized in the late 19th century by Werner.[3] Consequently, the homogeneous catalytic functionalization of NH3 remained elusive [4] until the recent discovery by Shen and Hartwig [5] and Surry and Buchwald [6] of the palladiumcatalyzed coupling of aryl halides with ammonia in the presence of a stoichiometric amount of a base. An even more appealing process would be the addition of NH3 to carbon–carbon multiple bonds, a process that would occur ideally with 100% atom economy.[7] Although various homogeneous catalysts, including alkali metals,[8] early [9] and late transition metals,[10] and d-[11] and f-block elements,[12] have been used to effect the so-called hydroamination reaction, none of them were reported to be effective when NH3 is used as the amine partner.[13] Herein we report that cationic gold (I) complexes supported by a cyclic (alkyl)(amino) carbene (CAAC)[14] ligand readily catalyze the addition of ammonia to a variety of unactivated alkynes and allenes to provide a diverse array of linear and cyclic nitrogencontaining compounds.We showed recently that the cationic CAAC–gold complex A was very robust and exhibited unusual catalytic reactivity towards alkynes.[15] This discovery prompted us to investigate whether such a complex could activate alkynes sufficiently to enable the addition of NH3.[16] Thus, excess ammonia was condensed into a sealable NMR tube containing A (5 mol%), 3-hexyne, and deuterated benzene. Upon heating to 160 C for 3.5 h, the clean addition of NH3 afforded the primary imine 2a, the expected tautomer of the corresponding enamine (Table 1).[17]