基于氢键活化的不对称有机催化碳碳键形成反应研究

基于氢键活化的不对称有机催化碳碳键形成反应研究 附件2 论文中英文摘要格式 作者姓名:陈 小 华 论文题目:基于氢键活化的不对称有机催化碳碳键形成反应研究 作者简介:陈小华，男，1981年3月出生，2003年9月师从于中国科学院成都有机化学研究所龚流柱教授，于2008年7月获博士学位。 中 文 摘 要 氢键活化的不对称有机小分子催化反应已成为不对称催化的一个热点领域。本论文基于“氢键活化(Hydrogen-Bonding Activation)”的概念，设计了多种具有氢键作用的有机小分子催化剂，成功实现了多种氢键活化模型，对多种不同的有机催化不对称反应，都能取得非常好的结果。 1. 手性Brønsted酸催化的Biginelli反应 设计合成新型的H-BINOL衍生的手性磷酸催化剂能够很好地催化Biginelli反应，首次8 实现了手性有机小分子催化的不对称Biginelli反应。H-BINOL衍生的3, 3’-位苯基取代的磷8 酸可以高效催化各类芳香醛或脂肪醛反应底物，能够得到很好的结果;在室温条件下，仅用10mol%的催化剂就可以获得最高达94% 收率和对映选择性高达97% ee的产物。同时，H-BINOL衍生的3,3’-位苯基取代的手性磷酸催化剂还可以催化以丙酰乙酸酯为底物的8 Biginelli-Type反应，最高可以获得70%的收率和93% ee的对映选择性。利用我们发展的手性磷酸催化的Biginelli反应方法学可以高效地合成一些具有强生理活性的化合物或中间体，通过简单的反应可以合成具有高光学纯度的药用分子Monastrol。该催化体系反应过程中避免金属参与，这为直接合成具有光学活性的3, 4-二氢嘧啶-2-酮衍生物，提供了最实用的方法;同时该催化体系为进行多样性导向的生理活性化合物合成，提供了实用可行的方法。在机理研究方面，对手性磷酸催化的Biginelli反应的活化模型进行了初步的探讨，提出了的催化剂和底物的双活化作用模型。 2. 手性Brønsted酸催化三组分1,3-偶极环加成反应 首次发现了手性磷酸催化甲亚胺叶立德和贫电子烯烃的高对映选择性的不对称1, 3-偶极环加成反应。通过引入分子内氢键,发展了一类新的手性磷酸催化剂——手性双磷酸催化 剂;提出了用手性磷酸和甲亚胺叶立德通过氢键作用，形成手性活泼中间体来控制反应立体选择性的概念。手性双磷酸催化的不对称三组分1, 3-偶极环加成反应，在非常温和的条件下，对各类底物能够得到单一构型，高达99%ee的对映选择性。同时，对于吡咯环2-位是季碳四个手性中心的产物也能取得高达97%ee的对映选择性。该催化体系可以方便地得到高光学活性的多取代吡咯衍生物，为进行多样性导向的强生理活性化合物合成提供了很好的方法学。该研究工作大大地拓展了小分子催化剂的结构类型，同时拓展了以氢键活化的不对称有机催化反应类型;利用Brønsted 酸催化体系活化1, 3-偶极的概念，为发展其它不对称1, 3-偶极环加成反应提供了新思路。同时,发现手性磷酸可以很好地催化醛、氨基酯、芳香胺的不对称三组份1, 3-偶极环加成反应，该催化体系能够在非常温和的条件下，得到高达(91/9 dr, 98% ee) 选择性的多取代手性咪唑烷类衍生物，该方法学为手性二胺的合成提供了简单实用的方法。通过对反应机理的研究，发现两分子的手性磷酸参与活化反应中间体甲亚胺叶立德和亚胺。这部分研究工作拓展了手性Brønsted 酸催化的不对称反应类型。 发展了手性磷酸催化甲亚胺叶立德与羟吲哚衍生的,, ,-不饱和化合物的不对称三组分1, 3-偶极环加成反应，可以直接获得高达99/1的区域选择性和98%ee的对映选择性的螺环生物碱衍生物，首次实现了直接不对称催化合成螺环生物碱骨架。该反应获得与手性诱导方法学不同区域选择性的化合物，这可以为合成具有强生理活性的手性螺环生物碱提供有效的方法。利用该方法学可以合成的结构多样性螺环生物碱衍生物;这对新一类抗肿瘤药物的发现和构效关系的研究，以及开展该类化合物的化学生物学的研究具有重要意义。 3. 脯氨酰胺催化的水相直接Aldol反应 通过系统研究催化剂结构和反应区域选择性及对映选择性的关系，发现带有两个酯基的L-脯氨酰胺能够选择性地催化醛与羟基丙酮的水相不对称直接Aldol反应得到1,4 二醇为主的加成产物，有效地控制了反应的区域选择性，而且有很好的立体控制能力。该催化体系催化醛与羟基丙酮的水相Aldol反应可以获得高达95/5区域选择性和高达99% ee的对映选择性;无论是区域选择性还是对映选择性相比寡肽催化剂都有很大的提高，具有底物普适性，这一结果也是目前同类水相反应中最好的。L-脯氨酰胺催化羟基丁酮和氟代丙酮作给体的水相Aldol反应也能获得很好的区域选择性和高达96% ee的对映选择性。1，4 二醇化合物在有机合成中是非常有用的光学活性中间体，经过简单的几步反应可以合成多种具有生理活性的化合物，3,5-二取代的四氢呋喃衍生物和2, 4-二羟基-4-联苯基丁酸。通过理论化学计算发现，水分子和脯氨酰胺羰基上的氧及底物羟基丙酮羟基上的氢原子形成双氢键，提出了“水-双氢键”过渡态作用模型;“水-双氢键”不但控制了区域选择性性，而且稳定了反应过渡态; 该过渡态模型很好地解释了实验结果。通过水相Aldol反应的研究及“水-双氢键”过渡态模 型机理的阐述，为新型有机小分子催化剂的设计，理解酶催化的机理及在水相中进行仿酶催 化提供了新的思路。 关键词: 氢键活化， 不对称有机催化， Biginelli反应， 1, 3-偶极环加成反应， 水相直接Aldol反应 Asymmetric Organocatalytic Carbon-Carbon Bond-Forming Reactions By Hydrogen-Bonding Activation Chen Xiao-Hua ABSTRACT Enantioselective synthesis with small-molecule chiral hydrogen-bond donors has emerged as a frontier of research in the field of asymmetric catalysis. In this dissertation, we have focused on the concept of Hydrogen-Bonding Activation, and have designed chiral hydrogen-bond donors as a broadly applicable class of catalysts for enantioselective synthesis. 1. Highly Enantioselective Organocatalytic Biginelli Reaction: A series of binol- and H-binol-based phosphoric acids have for the first time been evaluated 8 for their ability to catalyze Biginelli reactions of aldehydes, thiourea, and ,-keto esters. A new chiral phosphoric acid, derived from 3,3’-diphenyl-H-binol, exhibited superior catalytic activity 8 and enantioselectivity compared to its structural analogues, affording high enantioselectivities ranging from 85% to 97% ee with a wide scope of substrates. A metal-free preparation of optically active Monastrol was achieved on the basis of the current process. This reaction has an advantage of avoiding the contamination of transition metals in the manufacture of the medicinally relevant chiral 3,4-dihydropyrimidin-2-(1H)-ones. The Mechanism Considerations based on the results observed experimentally and theoretical calculations on the transition states of the stereogenic center forming step showed that the imine and enol were simultaneously activated by the bifunctional chiral phosphoric acid through formation of hydrogen bonds. 2. Asymmetric Organocatalytic Three-Component 1,3-Dipolar Cycloaddition: The first Brønsted acid-catalyzed three-component asymmetric 1,3-dipolar addition reaction between aldehydes, amino esters, and dipolarophiles by a new bis-phosphoric acid derived from the linked BINOL, furnishing multiply-substituted pyrolidines in high yield with excellent enantioselectivities under mild conditions. The procedure is easy to perform and allows a rapid, diversity-oriented, and enantioselective synthesis of pyrolidine derivatives. The concept that the stereoselectivity may be controlled by use of a chiral Brønsted acid-bonded dipole may lead to new findings in asymmetric catalytic 1,3-dipolar addition reactions with dipolarophiles other than electron-deficient olefins. we also disclosed the first catalytic asymmetric 1,3-dipolar cycloaddition that directly assembles aldehydes, amino esters, and anilines into synthetically useful chiral imidazolidines with high levels of stereoselectivity. Two molecules of Brønsted acids participated in the catalysis by the activation of both azomethine ylides and imines. This reaction has further demonstrated that the chiral Brønsted acid activated dipoles are versatile intermediates for the creation of new enantioselective 1,3-dipolar cycloadditions. We have disclosed the the first asymmetric catalytic 1,3-dipolar cycloaddition between azomethine ylide and methyleneindolinones with concomitant creation of two adjacent quaternary [7]stereogenic centers, for the rapid synthesis of spiro [pyrrolidin-3,3'-oxindole] derivatives with high enantiopurity and structural diversity. In addition, this reaction proceeded with reversal of the normal regioselectivity controlled by electronic effect. This reaction provides so far the sole catalytic synthesis of spiro [pyrrolidin-3,3'-oxindole] derivatives with high enantioselectivity and structural diversity, and thus, would be highly valuable to pharmaceutically relevant fields. This reaction has further demonstrated that the chiral Brønsted acid activated dipoles are versatile intermediates for the creation of new enantioselective 1, 3-dipolar cycloadditions. 3. Organocatalyzed Highly Enantioselective Direct Aldol Reactions of Aldehydes with Ketone in Aqueous Media: An organocatalyst prepared from (2R, 3R)-diethyl 2-amino-3-hydroxysuccinate and L-proline exhibited high regio- and enantioselectivities for the direct aldol reactions of hydroxyacetone and fluoroacetone with aldehydes in aqueous media. It was found that water could be used to control the regioselectivity. The presence of 20-30 mol% of the catalyst afforded the direct aldol reactions of a wide range of aldehydes with hydroxyacetone to give the otherwise disfavored products with excellent enantioselectivities ranging from 91% to 99% ees and high regioselectivities. Aldolizations of fluoroacetone with aldehydes mediated by 30 mol% of the organocatalyst in aqueous media preferentially occurred at the methyl group, yielding products with high enantioselectivities (up to 91% ee), however, dominantly took place at the fluoromethyl group in THF. Optically active 3, 5-disubstitued tetrahydrofurans and 2S, 4R-dihydroxy-4-biphenylbutyric acid were prepared starting with the aldol reaction of hydroxyacetone. Theoretical studies on the role of water in controlling the regioselectivity revealed that the hydrogen bonds formed between the amide oxygen of proline amide, hydroxy of hydroxyacetone and water is responsible for the regioselectivity by microsolvation with explicit water molecule as hydrogen bond donor and/or acceptor. Key words: Hydrogen-Bonding Activation, Asymmetric Organocatalysis, Asymmetric Biginelli Reaction, 1, 3-Dipolar Addition, Asymmetric Direct Aldol reaction