A NEW APPROACH TO SELECTIVE NOBLE METAL CATALYSTS

选择性贵金属催化剂的新方法

• 批准号: 6701771
• 负责人: MICHEL R GAGNE
• 金额: $ 19.04万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-02-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6701771
• 关键词: alkenes; catalyst; chemical synthesis; ketones; metal complex; molecular shape; molecular size; phosphines; platinum; protonation; stereochemistry; titanium

This proposal describes a conceptually new approach to asymmetric catalyst design. Traditional asymmetric catalysts rely on chiral ancillary ligands coordinated to the metal (inner sphere) to provide stereocontrol. We propose to influence selectivity through rational modification of a catalyst's outer sphere, a strategy inspired by enzymatic mechanisms for controlling catalysis. Molecular imprinting of square planar platinum (II) complexes into rigid and porous organic polymers, followed by selective removal of a noncrosslinked chiral ligand from the modular template, reveals a kinetically robust chiral cavity that is intimately assoicated with the reactive coordination sites on the catalytic center. This cavity provides the outer-sphere environment for selectivity control, and is a natural mix of molecular recognition and asymmetric catalysis. The goals of this proposal are to: 1) Fundamentally understand outer-sphere stereocontrol. Can the outer-sphere be harnessed to control reaction selectivities? Enzyme analogies and preliminary data suggest it can. 2) Synthesize selective noble metal asymmetric catalysts that function via a combination of inner- and outer-sphere stereocontrol elements. Molecular imprinting will yield novel catalysts for the enantioselective hydrogenation of alkenes and ketones, and the enantioselective sp2-sp2 and sp2-sp3 cross coupling reactions. Built into the imprinting strategy is the flexibility to: a) orient functional groups within the associated cavity for transition state (pre)organization, and b) modify the phosphine ligand to access novel electron rich catalysts. Our targeted reactions are important for the synthesis of new chiral feedstocks that will eventually reduce our reliability on the chiral pool. Moreover, our approach to generating enantioselective catalysts utilizes inexpensive achiral diphosphines and results in heterogenized catalysts there are valuable in medicinal and process research as well as bulk fine chemical synthesis. Increased commercial availability of chiral precursors will aid in drug discovery and pharmaceutical process synthesis.

该建议描述了一种概念上的新方法来设计不对称催化剂。 传统的不对称催化剂依赖于与金属（内球）配位的手性辅助配体来提供立体控制。 我们建议通过合理修改催化剂的外层来影响选择性，这是一种受酶机制控制催化作用启发的策略。 正方形平面铂（II）配合物到刚性和多孔的有机聚合物的分子印迹，然后从模块化模板的非交联的手性配体的选择性去除，揭示了一个动力学稳健的手性腔，是密切assoicated与催化中心上的反应性配位位点。 该空腔为选择性控制提供了外层环境，并且是分子识别和不对称催化的天然混合物。本研究的目的是：1）从根本上理解外层空间立体控制。 外层能否用来控制反应的选择性？ 酶的类比和初步数据表明它可以。 2)合成选择性贵金属不对称催化剂，其通过内外球立体控制元素的组合起作用。 分子印迹技术将为烯烃和酮的不对称加氢以及不对称的sp2-sp2和sp2-sp3交叉偶联反应提供新的催化剂。 嵌入到压印策略中的是以下灵活性：a）在相关空腔内定向官能团以用于过渡态（预）组织，和B）修饰膦配体以获得新颖的富电子催化剂。我们的目标反应对于合成新的手性原料非常重要，这最终会降低我们对手性池的可靠性。 此外，我们的方法来产生对映选择性催化剂利用廉价的非手性双膦和结果的多相催化剂有价值的医药和工艺研究，以及大量的精细化学合成。 手性前体的商业可用性的增加将有助于药物发现和制药工艺合成。