New strategies for asymmetric photocatalysis: asymmetric organocatalytic/photoredox relay catalysis for efficient synthesis of polycyclic compounds containing vicinal amino alcohols

An asymmetric catalytic strategy in photocatalysis utilizing a chirality-induced approach through an organocatalytic/photoredox relay catalysis strategy is successfully achieved for the rapid construction of polycyclic compounds containing vicinal amino alcohols in a one-pot protocol. This methodology facilitates the efficient synthesis of diverse substituted polycyclic tetrahydroquinoline and benzofuran-derived vicinal amino alcohols, each containing five consecutive chiral centers, with high yields,excellent diastereoselectivities and enantioselectivities(up to 95% yield, >20:1 dr and 98% ee), under mild reaction conditions driven by sequential bifunctional squaramide organocatalyst-catalyzed [4+2] annulation and photocatalyst-catalyzed ketyl radical addition cyclization reaction process. Furthermore, investigations into the stereoselectivity mechanism and high-resolution mass spectrometry(HRMS) experiments on free radical trapping have provided evidence for elucidating the detailed mechanism of chirality-induced processes and chiral intermediate conversions in this procedure.

Stereodivergently asymmetric synthesis of chiral phosphorus compounds by synergistic combination of ion-pair catalyst and base

Stereodivergently constructing the designed products having adjacent multi-stereocenters via a given reaction,with excellent control of both absolute and relative configurations,presents one of the substantial hurdles in asymmetric catalysis.Herein,we report a precisely stereodivergent asymmetric protocol by synergistic combination of phosphonium-involved ion-pair catalysis and base for accessing to chiral phosphorus compounds bearing two adjacent chiral centers particularly containing an acidic protonated enantioenriched carbon atom,having broad functional group compatibility in both dynamic and thermodynamic processes under mild reaction conditions.Two keys for the success in constructing these stereoisomers with high levels of regio-,diastereo-,and enantioselectivities were contained:firstly,the precise stereo-control in providing dynamic products was enabled by bifunctional phosphonium salt catalyst with semi-enclosed cavity;secondly,the readily stereospecific transformation of adducts from dynamic to thermodynamic version was initiated by achiral base.All four stereoisomers could be readily accessed even in gram-scale in high yields with maintaining excellent stereoselectivities,illustrating the potential of this synergistic catalytic methodology in organic synthesis.Moreover,mechanistic studies including density functional theory(DFT)calculations and control experiments provide insights into the mechanism.

Production of Chiral Aromatic Alcohol by Asymmetric Reduction with Vegetable Catalyst

Chiral aromatic alcohols are the key chiral building block for many important enantiopure pharmaceu-ticals. In this work,we studied asymmetric reduction of prochiral aromatic ketone to produce the corresponding chiral alcohol using vegetables as the biocatalyst. Acetophenone was chosen as the model substrate. The results in-dicate that acetophenone can be reduced to the corresponding chiral alcohols with high enantioselectivity by the chosen vegetables,i.e. apple(Malus pumila),carrot(Daucus carota),cucumber(Cucumis sativus),onion(Allium cepa),potato(Soanum tuberosum),radish(Raphanus sativus),and sweet potato(Ipomoea batatas) . In the reaction,R-1-phenylethanol is produced with apple,sweet potato and potato as the catalyst,while S-1-phenylethanol is the product with the other vegetables as the catalyst. In term of the enantioselectivity and reaction yield,carrot(D. ca-rota) is the best catalyst for this reaction. Furthermore,the reaction characteristics were studied in detail using car-rot(D. carota) as the biocatalyst. The effects of various factors on the reaction were investigated and the optimal reaction conditions were determined. Under the optimal reaction conditions(reaction time 50 h,substrate concen-tration 20 mmol·L-1,reaction temperature 35 °C and pH 7),95% of e.e.(to S-1-phenylethanol) and 85% chemical yield can be obtained. This work extends the biocatalyst for the asymmetric reduction reaction of prochiral aromatic ketones,and provides a novel potential route to produce enantiopure aromatic alcohols.

Enantioselective Reduction of Achiral Ketones with NaBH_4/I_2 Catalyzed by (S)-Ferrocenyl Amino Alcohols

The reduction reagents prepared from sodium borohydride, I-2 and a catalytic amount of chiral ferrocenyl amino alcohols 2a-e have been successfully applied to the enantioselective reduction of ketones. The optically active secondary alcohols were obtained in moderate enantiomeric excess and high chemical yield.

Radicals as Chiral Catalysts for Asymmetric Radical Cyclization Reactions

Due to the innate highly reactive properties and short life-time,organic free radicals can often serve as promoters or intermediates to engage in various radical transformations,which are often otherwise difficult to access by ionic pathway-based mechanisms.With the evolvement of radical chemistry,chiral radical catalyzed-transformations have recently emerged as an attractive and robust platform for synthesis of chiral molecules of interest.Herein,we highlight several creative and strategic advances in chiral radical catalyst design,cyclization reaction achievements,and future challenges.

Carbene-Catalyzed Asymmetric Ring-Opening Reaction of Biaryl Lactams to Access Axially Chiral Biaryls

Axially chiral biaryls represent the most important class of atropisomers,and they widely exist in natural products and biologically active molecules.They also constitute a unique scaffold for chiral ligands and catalysts in organic synthesis.The development of synthetic methods to obtain such chiral compounds has received widespread attention,among which catalytically atroposelective ring-opening of configurationally labile compounds represents one of the most attractive strategies.Various substrates with strained cyclic structures,such as the renowned Bringmann's lactones,can undergo asymmetric transformation into stable atropisomers.Known advancement primarily relies on metal catalyst combined with well-designed chiral ligands,the approaches utilizing organocatalysis as a critical resolution strategy are notably scarce.In this study,we disclosed a N-heterocyclic carbene(NHC)-catalyzed asymmetric ring-opening reaction of biaryl lactams via direct atroposelective nucleophilic activation.The optimized bulky carbene catalyst ensures that the reaction can proceed under mild conditions,affording the desired product with good to excellent yields and atroposelectivity.

Visible Light-Mediated Cobalt and Photoredox Dual-Catalyzed Asymmetric Reductive Coupling for Axially Chiral Secondary Alcohols

Secondary alcohols bearing both axial and central chirality comprise attractive biological activity and exhibit excellent chiral induction in asymmetric reactions.However,only very limited asymmetric catalytic approaches were developed for their synthesis.We herein describe visible light-mediated cobalt-catalyzed asymmetric reductive Grignard-type addition of aryl iodides with axially prochiral biaryl dialdehydes leading to the direct construction of axially chiral secondary alcohols.Preliminary mechanistic studies indicate that efficient kinetic recognition of diastereomers might occur for axially prochiral dialdehydes to improve the stereoselectivity,which might open a new avenue for the challenging cascade construction of multiple chiral elements.This protocol features excellent enantio-and diastereoselectivity,green and mild conditions,simple operation,and broad substrate scope,providing a modular platform for the synthesis of secondary axially chiral alcohols.

Atroposelective Synthesis of 2-Arylindoles via Chiral Phosphoric Acid-Catalyzed Direct Amination of Indoles

Indole-based atropisomers are a very important class of axially chiral compounds.However,the atroposelective synthesis of axially chiral 2-arylindole remains largely unexplored.In this study,we report the successful synthesis of atropisomeric 2-arylindoles using direct amination of indoles with p-quinonediimines in the presence of chiral phosphoric acid as a catalyst.Quinonediimine acts as an aminating reagent through formal polarity inversion of imine.The malonate group on the 2-aryl of 2-indoles was found to be essen-tial for high enantioselectivity of the products.This could be due to the additional interaction between the ester group and the cata-lyst,as well as the intramolecular hydrogen bonding.Our findings provide a new strategy for the asymmetric construction of 2-arylindole atropisomers.

手性磷酸催化非环状N,N′-缩酮的不对称合成

手性N,N′-缩酮是药物分子和生物活性化合物最重要的核心结构之一,也是有机合成中重要的催化剂或配体。因此,不对称合成N,N′-缩酮具有重要意义。通过手性磷酸、溶剂、催化剂负载量和投料比的筛选,确定了最佳的反应条件:在手性磷酸的催化下,以1,4-二氧六环作为溶剂,5-氨基异噁唑与β,γ-炔基-α-酮亚胺酯在室温下发生区域选择性的氮杂-曼尼希反应,实现异噁唑的不对称N—H烷基化,以中等至良好的收率(46%~83% yield)和较好的对映选择性(82%~92%ee)合成非环状的N,N′-缩酮。所有产物结构由^(1)H NMR,^(13)C NMR和HR-MS(ESI)确证,绝对构型通过X-射线晶体结构分析确定。

Pinacol coupling going in a photocatalytic asymmetric manner:construction of chiral vicinal amino alcohols

Vicinal amino alcohols are a class of important motifs in pharmaceuticals,natural products as well as wide application in asymmetric catalysis（Scheme 1（a））.It is no doubt that development of efficient methods to access them has been a prominent research topic in the past decades.

(S)-普萘洛尔的合成、应用及剂型研究进展

(S)-普萘洛尔是一种重要的β受体阻滞剂,用于治疗心血管疾病、焦虑症、甲状腺功能亢进等多种疾病。本文综述了迄今为止用于制备(S)-普萘洛尔的化学合成方法,如不对称拆分法、手性源合成法和不对称催化法。讨论了(S)-普萘洛尔口服和外用等多种新剂型,以及(S)-普萘洛尔在心血管疾病、焦虑症、甲状腺功能亢进、特发性震颤等疾病上的应用。本文期望为(S)-普萘洛尔的合成方法、应用和剂型研究提供参考。

2-甲酰基-1,1′-联萘手性醛催化剂的合成

目前报道的手性醛催化剂(3)的合成路线总收率较低,不适用于大量合成。通过对3的合成路线进行改进,以(S)-1,1′-联二萘酚((S)-BINOL)为原料,经磺酰化、插羰反应、偶联反应、硼化、氧化、甲氧基甲基保护、还原、氧化、脱除甲氧基甲基以及溴化10步反应合成了手性醛催化剂(3a~3i),其中大部分化合物的总收率大于20%。该合成路线可放大到10 mmol规模来进行,具有一定的应用前景。

不对称催化构建轴手性化合物的研究进展

多数具有重要生理活性的天然产物和手性药物分子中都含具有轴手性骨架,研究如何构建具有轴手性化合物并将其应用于手性药物及天然产物的高效合成具有十分重大的实际意义。对联芳基、杂联芳基以及其他类型的轴手性化合物的研究进展进行了讨论,并对轴手性化合物的不对称催化合成策略作了重点介绍,同时举例说明所得轴手性化合物的潜在应用价值。

Enantiopure inherently chiral calix[4]arene derivatives containing quinolin-2-yl-methanol moiety:Synthesis and application in the catalytic asymmetric addition of diethylzinc to benzaldehyde

A series of novel N,O-type chiral ligands derived from enantiopure inherently chiral calix[4]arenes containing quinolin-2-yl-methanol moiety in the cone or partialcone conformation have been synthe-sized and characterized. Moreover,they have been applied to the catalytic asymmetric addition of diethylzinc to benzaldehyde,which represents the first example that the inherently chiral calixarene can be used as the chiral ligands for the catalytic asymmetric synthesis.

Asymmetric Synthesis of All Four Isomers of an Unusual Heterocycle-Containing Amino Acid ： 2-Amino-3-furan-2-yl-pentanoic Acid

All four isomers of a novel fl-branched unusual amino acid were designed and synthesized with high stereoselectivity （〉 90% de） and in 33%--44% overall yields by the use of 4（R/S）-5,5-dimethyl-4-phenyl-oxazolidin-2-one as the chiral auxiliary via asymmetric 1,4-Michael addition, direct or indirect azidation, hydrolysis and hydrogenation reactions.

(2 S,5 S)-2-(2-(二苯基膦基)苯基)-3,5-二取代基咪唑啉-4-酮的合成

随着金属催化不对称合成研究的兴起,研究人员对手性配体的需求日趋迫切,以简便的方式获得高效的手性配体一直是金属催化不对称反应研究的重点之一,其中包括含氮,磷等含杂原子的膦配体。这些配体广泛地用于C—C、C—N及C—O的构建和不对称氢化反应中,展现出了可观的研究及应用价值。以α-氨基酸为起始原料,在三光气作用下得到酸酐类中间体,随后经酰胺化、缩合两步反应,成功以26.4%~33.8%收率得到(2 S,5 S)-2-(2-(二苯基膦基)苯基)-3,5-二取代基咪唑啉-4-酮类化合物。

(R)-1-(3-(二苄基甲基氨基)-2-羟丙基)-1-甲基哌啶碘化铵的合成与应用

首先,以二苄胺和(R)-环氧氯丙烷为原料合成了(R)-3-二苄胺基-1,2-环氧丙烷,再与哌啶反应合成了(R)-1-二苄胺基-3-哌啶基-2-丙醇(ligand 1),并研究了ligand 1诱导二乙基锌对苯甲醛的对映选择性加成反应;其次,用(R)-1-二苄胺基-3-哌啶基-2-丙醇和碘甲烷反应合成了(R)-1-(3-(二苄基甲基氨基)-2-羟丙基)-1-甲基哌啶碘化铵(ligand 2),同时研究了ligand 2在不对称相转移催化反应中的应用,并利用核磁共振对上述产物进行了表征.试验结果显示,上述手性配体均具有一定的不对称诱导效果.

新型手性硫醚-亚磷酰胺配体的设计与应用

根据模块组合法,设计并合成了一种具有亚磷酰胺结构的硫醚配体,该配体具有原料便宜易得、合成步骤简单、易于修饰和结构稳定等特点。以配体/钯络合物催化的丙二酸二甲酯与1,3-二苯基烯丙基醋酸酯的烯丙基化反应作为模板反应,探究了溶剂和碱对其立体控制的影响。随后探究了中心手性与轴手性的匹配/错配现象以及硫醚片段的空间位阻和电性对反应立体控制的作用。在最佳条件下,产物的对映选择性能够达到-76%ee。

Enantioselective Alkylation of Aldehydes with Organoborons Enabled by Nickel/N-Heterocyclic Carbene Catalysis

Transition-metal-catalyzed asymmetric alkylation of aldehydes represents a straightforward strategy for the synthesis of chiral secondary alcohols.However,efficient methods using organoborons as coupling reagents are rare.Herein,we report a highly enantioselective nickel-catalyzed alkylation reaction of aldehydes,using readily available alkylborons as nucleophiles.A wide variety of chiral secondary alcohols were prepared from commercially available aldehydes with high yields.The key to the excellent enantioselectivity and chemoselectivity was the employment of a bulky C2-symmetric chiral NHC ligand.This protocol features excellent enantiocontrol,mild conditions,and good functional group compatibility.

Magnetic wrinkled organosilica-based metal-enzyme integrated catalysts for enhanced chemoenzymatic catalysis

Core-shell structured magnetic wrinkled organosilica-based metal-enzyme integrated catalysts were synthesized,and their catalytic performances were studied in the chemoenzymatic dynamic kinetic resolution of chiral amines in an organic solvent,as well as in the chemoenzymatic synthesis of chiral alcohols in water.Structureperformance studies revealed the important influence of their tunable structure and composition on the optimization of activity,stability,and recyclability in chemoenzymatic catalysis.