手性膦过渡金属配合物催化不对称交叉偶联反应的研究

自1973年Consiglio和Botteghi首次报道用(一)-DIOP的NiCl_2配合物催化芳基或乙烯基卤代物与仲烷基卤化镁交叉偶联生成光学活性的偶联产物以来,化学家们对不对称交叉偶联反应进行了深入研究。Hayashi等用手性二茂铁膦和手性β-氨基烷基膦的NiCl_2和PdCl_2配合物催化1-苯基乙基氯化     

手性助剂控制的不对称Michael加成立体选择性研究

手性助剂控制的不对称反应是不对称合成的主要方法之一.采用不同空间位阻Evans手性助剂对呋喃基丙烯酸进行立体选择性控制,通过不同空间位阻的格氏试剂对Michael受体1进行不对称1,4-Michael加成反应研究,合成了一系列新的Michael加成产物2a～2h.研究结果表明手性助剂及格氏试剂的空间位阻是影响反应立体选择性的主要因素.当手性助剂及格氏试剂的取代基为芳基时,产物的de值都大于95%,而取代基为烷基、苄基及脂环基时,产物的de值则低于70%.     

面手性二芳基膦-噁唑啉配体的开发及其在不对称催化反应中的应用

膦-噁唑啉配体形成的催化剂具有出色的催化活性和对映选择性, 被广泛应用于各种不对称催化反应中. 具有面手性的膦-噁唑啉配体是其中重要的一类. 综述了面手性二芳基膦-噁唑啉配体的开发, 并按反应类型介绍了它们在不对称催化反应中的应用.     

铜催化的立体选择性Doyle-Kirmse反应

以重氮化合物和烯丙基硫醚/炔丙基硫醚为反应底物,通过手性辅基和大位阻配体的不对称双诱导策略,高对映选择性地实现了经由铜卡宾产生硫叶立德的不对称[2,3]-σ重排反应(Doyle-Kirmse反应).脱除手性辅基后反应最高可以得到96%ee对映选择性.机理探究实验表明,反应很可能经历了自由的叶立德重排过程.该反应被进一步应用到含手性中心烯丙基硫醚的动力学拆分中.     

钯催化对映选择性合成2-芳基2-环己烯-1-酮轴手性化合物:多样性合成轴手性联芳基化合物的平台分子

正Angew.Chem.Int.Ed.2017,56,4777~4781联芳基轴手性化合物广泛分布于天然产物中,同时也是众多优势配体或催化剂的核心骨架.目前氧化偶联和芳基-芳基的交叉偶联反应是最直接构建联芳基轴手性化合物的方法,但常具有较大的底物局限性.如底物邻位取代     

钯卡宾参与的烯基芳烃轴手性化合物的合成

正Angew.Chem.Int.Ed.2016,55,2186~2190轴手性化合物因其具有独特的不可旋转的手性轴,在不对称催化等方面中有非常重要的应用.构建轴手性化合物最直接的方法之一是过渡金属催化的多组分的交叉偶联.中国科学技术大学顾振华课题组通过钯催化的溴代芳烃与腙化合物的偶联反应,以优异的产率得到了高对映选择性(ee约97%)的烯基芳烃轴手性化合物.反应通过芳基钯物种与卡宾形成钯卡宾中间体,最后迁移插入得到季碳钯物种,β-氢消除得到产物同时控制手性的产生.反应产率高,底物适用性好.产物可方便地转化为烯基膦配体(99%ee),并成功应用于不对称的烯丙基取代反应.     

组合铜催化的双氮芳基化及相分离高光学选择性合成双内酰胺螺环结构

<正>Angew.Chem.Int.Ed.2015,54,10917~10920螺环骨架是许多重要的天然产物以及药物分子中的关键结构,由于其独特的结构特征和高难度的合成挑战而备受关注.双内酰胺螺环及衍生物结构可以作为重要的离子载体以及手性辅基等,这类结构文献报道可以通过过渡金属催化2,2-二(邻卤代芳基)丙二酰胺化合物的分子内双N-芳基化偶联合成.但由于2,2-二(邻卤代芳基)丙二酰胺本     

不对称构筑二芳基次甲基立体中心的研究进展

二芳基次甲基结构单元广泛存在于具有重要生理和药理活性的天然产物和药物当中. 同时, 该结构单元中所特有的二芳基次甲基立体中心的对映选择性构筑往往也是天然产物全合成的难点和挑战性所在. 因此, 引起了众多有机合成化学家的研究兴趣. 近年来, 该手性立体中心的构建方法发展迅速, 新方法和新反应的报道也层出不穷; 开发出来的一些高效催化剂, 展示出独特的催化活性和选择性. 本文根据反应类型的不同, 将其分为不对称共轭加成反应和不对称氢化反应等六类, 综述近十年来二芳基次甲基立体中心的不对称构建方法及相关方法在天然产物全合成中的应用. 最后, 从全合成的角度进一步总结和分析未来构建二芳基次甲基手性立体中心的发展趋势, 力求发展更加高效、避免贵金属的催化剂及环境友好型的新方法和新试剂.     

亮点介绍

<正>镍氢催化的烯烃移位接力不对称氢烷基化Angew. Chem. Int. Ed. 2019, 58, 1754～1758C(sp~3)立体手性中心广泛存在于药物分子和天然产物中.构建C(sp~3)—C(sp~3)键的过程中,对映选择性地引入一个不对称的二级烷基官能团能构建有机分子中最常见的叔碳C(sp~3)立体手性中心,该转化简洁而富挑战.从消旋的烷基卤化物或者烷基金属试剂出发,过渡金属催化的立体归一性的偶联反应是实现这类不对称转化的实用策略之     

催化杂Diels-Alder反应的手性催化剂研究进展

不对称杂Diels-Alder反应为合成高区域选择性和立体选择性杂环化合物提供了重要途径，要实现杂Diels-Alder反应的不对称诱导，通常采取在二烯体或亲二烯体上连接手性辅基的方法，虽然可以获得高对映选择性环加成产物，但存在手性辅基用量大、且反应后与产物的分离复杂等缺点。近年来，手性催化剂因用量少以及对反应高选择性等优点而引起人们关注，本文按手性配体分类，简要综述了近年来不对称杂Diels-Alder反应中手性催化剂研究的新进展。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.