Hedberg Christian, Källström Klas, Arvidsson Per I, Brandt Peter, Andersson Pher G
Organic Chemistry, Department of Chemistry, Uppsala University, Uppsala, Sweden.
J Am Chem Soc. 2005 Nov 2;127(43):15083-90. doi: 10.1021/ja051920q.
The commercially available chiral diamine quincorine-amine, originally derived from quinine, was found to be a highly active catalyst for ruthenium-catalyzed hydrogenation of ketones. The complex formed between the quincorine-amine, containing both a primary and a quinuclidine amino function, and RuCp*Cl catalyzes the hydrogenation of aromatic and aliphatic ketones in up to 90% ee approximately 24 times faster than previously reported Ru-diamine complexes. The pseudo-enantiomer of the quincorine-amine, i.e., quincoridine-amine, also showed high activity; however, the enantioselectivities obtained with this catalyst were lower. The reason for the lower, but opposite stereoselectivity seen with the quincoridine-amine, as compared to the quincorine-amine, was rationalized by a kinetic and computational study of the mechanism of the reaction. The theoretical calculations also revealed a significantly lower activation barrier for the alcohol-mediated split of dihydrogen, as compared to the nonalcohol-mediated process, a finding of utmost implication also for the diphosphine/diamine-mediated enantioselective hydrogenation of ketones.
市售的手性二胺奎宁环胺最初源自奎宁，它被发现是钌催化酮氢化反应的一种高活性催化剂。含有伯氨基和奎宁环氨基官能团的奎宁环胺与RuCp*Cl形成的配合物催化芳香族和脂肪族酮的氢化反应，对映体过量值高达90%，其催化速度比先前报道的钌-二胺配合物快约24倍。奎宁环胺的假对映体，即奎宁定胺，也表现出高活性；然而，用这种催化剂获得的对映选择性较低。通过对反应机理的动力学和计算研究，解释了与奎宁环胺相比，奎宁定胺的对映选择性较低但相反的原因。理论计算还表明，与非醇介导的过程相比，醇介导的氢分子分裂的活化能垒显著更低，这一发现对二膦/二胺介导的酮对映选择性氢化反应也具有极其重要的意义。
