Catalytic Asymmetric Hydrogenation of Ketones Using non-Phosphine-Based N4 Ligands

自1987年Ru(OCOCH-3)-2(binap)/HCl复合催化剂首次亮相以来，使用手性二膦-Ru（II）配合物进行酮类均相不对称加氢已被确立为合成光学活性仲醇的最可靠策略之一。很明显，BINAP开创了一种趋势。钌体系，大量的氢化活性钌配合物与三价磷连接原子已被报道。对其有效性进行了检验，并与“特权”BINAP系统及其衍生产品进行了比较。相比之下，非膦基Ru配合物的不对称加氢反应仍处于发展阶段。我们设计并合成了Ph-BINAN-H-Py（3,3 '-Ph, Ph-N2, N2'-双（吡啶-2-甲基）- 1,1 '-联萘- 2,2 '-二胺），其特点是a) sp^3N内/ sp^2N外，b)供体-受体双功能，c)顺式选择性形成八面体金属配合物。配体在芳香酮与钌π烯丙基前体的不对称加氢反应中的应用已经得到证实。反应定量进行，S/C比超过10000，对映体选择性高达99:1。非膦配体的成功应用为不对称氢化化学开辟了一条新的道路。

Homogeneous asymmetric hydrogenation of ketones using chiral diphosphine-Ru(II) complexes has been established as one of the most reliable strategies for the synthesis of optically active secondary alcohols since our Ru(OCOCH-3)-2(binap)/HCl combined catalyst made its debut in 1987. Having apparently started a trend with BINAP. Ru systems, a tremendous number of hydrogenation-active Ru complexes with trivalent phosphorus ligating atoms have been reported. The effectiveness has been examined and compared with the" privileged" BINAP system and its derivatives. In comparison, asymmetric hydrogenation using non-phosphine-based Ru complexes is still in the developmental stage. We have designed and synthesized Ph-BINAN-H-Py(3, 3'-Ph, Ph-N2, N2'-bis(pyridin-2-ylmethyl)-1, 1'-binaphthyl-2, 2'-diamine) which is characterized by a) inside sp^3N/outside sp^2N, b) donor-acceptor bifunctional ability, and c) cis-alpha-selective formation of octahedral metal complexes. The utility of ligands has been demonstrated in asymmetric hydrogenation of aromatic ketones in combination with a Ru-π-allyl precursor. The reaction quantitatively proceeds with the S/C ratio of over 10, 000 with up to 99 : 1 enantioselectivity. The success using non-phosphine ligand has made a new trail to asymmetric hydrogenation chemistry.