Soluble Polymer-Supported Synthesis of α-Amino Acid Derivatives

Due to the central role played by α-amino acid in chemistry and biology, the development of versatile and new methodology for the synthesis of natural and unnatural α-amino acid has emerged as an important and challenging synthetic endeavour for organic chemists.[1] Among the various methodologies reported for α-amino acid synthesis, [2,3] the solid-phase organic synthesis (SPOS) has served as an important approach. [4] However, inherent prob lems on solid supports are reactive site accessibility, site-site interaction and monitoring of the reaction.     

Nmr analysis of α-methyl branched organic acids

A methode for analyzing α-methyl branched organic acids has been developed using NMR spectroscopy. The composition is determined in terms of α,α-dimethyl, α-methyl-α-alkyl and α-methyl strnetures. Peak assignmunts were made on the basis of model compound studies. This technique has been successfully used in analyzing Koch acid synthesis mixtures.     

α-羟基取代膦酸酯类化合物的合成研究进展

含磷化合物一直是有机化学研究的热点之一,许多合成药物以及天然产物都含有磷原子。其中,α-羟基取代膦酸酯类化合物是重要的有机合成中间体,其在有机合成中的应用一直受到广泛关注。文章详细综述了α-羟基取代膦酸酯类化合物的合成方法。     

Uncatalyzed and solvent-free one-pot three component synthesis of α-amino phosphonates

An innovative route to preaper a number of variously substituted α-aminophosphonate is presented. The protocol avoids the use of any catalyst, organic solvents, and dry reaction conditions. The synthesis of α-aminophosphonates in the present study represents a three-component reaction in which no intermediate formation of either an imine or α-hydroxy phosphonate was observed.     

Photocatalytic α-Tertiary Amine Synthesis via C−H Alkylation of Unmasked Primary Amines

A practical, catalytic entry to α,α,α-trisubstituted (α-tertiary) primary amines by C−H functionalisation has long been recognised as a critical gap in the synthetic toolbox. We report a simple and scalable solution to this problem that does not require any in situ protection of the amino group and proceeds with 100 % atom-economy. Our strategy, which uses an organic photocatalyst in combination with azide ion as a hydrogen atom transfer (HAT) catalyst, provides a direct synthesis of α-tertiary amines, or their corresponding γ-lactams. We anticipate that this methodology will inspire new retrosynthetic disconnections for substituted amine derivatives in organic synthesis, and particularly for challenging α-tertiary primary amines.     

绿色路易斯酸三卤化铟在有机合成中的应用

三卤化铟作为温和的路易斯酸可在水、醇等绿色溶剂中实现高化学选择性、高 区域选择性和高立体选择性的化学转化。综述了三卤化铟在羟醛反应和类羟醛-曼 尼希反应、Fiedel-Crafts反应、环氧化合物的重排反应、α-氨基膦酸的合成、喹 啉环系的构建、酯交换反应、Diels-Alder反应和杂Diels-Alder反应,手性呋喃二 醇的合成、水相中的叠氮解反应和二硫缩醛的制备中的应用,同时还总结了本课题 组将三卤化铟应用于Biginelli反应和还原脱氧反应的反应结果。三卤化铟在有机 合成中潜在的优势将推动“绿色化学”的发展。     

Stereoselective Synthesis of α-Aminonitril on Glucose Templates

Both proteinogenic and non proteinogenic α-amino acids are of particular interest as constituents of peptide factors, peptidomimetics and antibiotics for the construction of modern selective drugs. [1] Furthemore, α-amino acid derivatives are interesting building units for chiral-pool syntheses of enantiomerically pure natural products. [2] Numerous efforts in modern organic synthesis are centered on the synthesis of enantiomerically pure α-amino acids. [3] During the past three decades efficient methods of asymmetric synthesis of α-amino acids have been developed; most of them are based on electrophilic transformations of organometallic intermediates. [4] Using the concept that the chirality of the carbohydrates can be exploited for diastereoselective reactions, Kunz and his cooperator had developed a Strecker synthesis with glycosyl amines as chiral auxiliaries. [5]     

New general synthesis of α-alkoxyketones via α'-alkylation, α-alkylation and α,α'-dialkylation of α-alkoxyketimines

α-Methoxy- and α-ethoxyketones, as important intermediates in organic synthesis and flavor compounds in food chemistry, were synthesized by deprotonation of N-(1-alkoxy-2-propylidene)isopropylamine, prepared by condensation of the corresponding α-alkoxyacetone with isopropylamine, and subsequent reaction of the corresponding 1-azaallylic anions with alkyl halides to afford α'-alkylated, α-alkylated and α,α'-dialkylated ketimines. Hydrolysis of the imino function led to the desired substituted α-alkoxyketones. The ratio of α-, α'-, and α,α'-(di)alkylated compounds depended on the amount of base used and on the nature of the alkylating reagent.     

α-酮酸酯的合成研究进展

α-酮酸及其酯是一类双官能团化合物, 性质活泼而特殊, 是重要的有机合成、药物合成及生物合成中间体。文中扼要论述了近二十年来α-酮酸酯的合成研究进展。     

Enantioselective De Novo Synthesis of α,α-Diaryl Ketones from Alkynes

Chiral α,α-diaryl ketones are structural motifs commonly present in bioactive molecules, and they are also valuable building blocks in synthetic organic chemistry. However, catalytic asymmetric synthesis of α,α-diaryl ketones bearing a tertiary stereogenic center remains largely unsolved. Herein, we report a catalytic de novo enantioselective synthesis of α,α-diaryl ketones from simple alkynes via chiral phosphoric acid (CPA) catalysis. A broad range of enolizable α,α-diaryl ketones are prepared in good yields and with excellent enantioselectivities. The described protocol also serves as an efficient deuteration method for the preparation of enantiomerically enriched deuterated α,α-diaryl ketones. Using the methodology reported, bioactive molecules, including one of the best-selling anti-breast cancer drugs, tamoxifen, are readily synthesized.     

Direct Light-Enabled Access to α-Boryl Radicals: Application in the Stereodivergent Synthesis of Allyl Boronic Esters**

Operationally simple strategies to assemble boron containing organic frameworks are highly enabling in organic synthesis. While conventional retrosynthetic logic has engendered many platforms focusing on the direct formation of C−B bonds, α-boryl radicals have recently reemerged as versatile open-shell alternatives to access organoborons via adjacent C−C bond formation. Direct light-enabled α-activation is currently contingent on photo- or transition metal-catalysis activation to efficiently generate radical species. Here, we disclose a facile activation of α-halo boronic esters using only visible light and a simple Lewis base to enable homolytic scission. Intermolecular addition to styrenes facilitates the rapid construction of highly versatile E-allylic boronic esters. The simplicity of activation permits the strategic merger of this construct with selective energy transfer catalysis to enable the complimentary stereodivergent synthesis of Z-allylic boronic esters.     

Direct Synthesis of α-Amino Acid Derivatives by Hydrative Amination of Alkynes

α-Amino acid derivatives are key components of the molecules of life. The synthesis of α-amino carbonyl/carboxyl compounds is a contemporary challenge in organic synthesis. Herein, we report a practical method for the preparation of α-amino acid derivatives via direct hydrative amination of activated alkynes under mild conditions, relying on sulfinamides as the nitrogen source. Computational studies suggest that the reaction is enabled by a new type of sulfonium [2,3]-sigmatropic rearrangement.     

2-碘酰基苯甲酸在有机合成中的研究与应用

高价有机碘化合物的反应性质与过渡金属相似,其参与的反应具有反应条件较温和、选择性好、产率高及环境友好等优点,因而近年来关于高价有机碘试剂的研究受到广泛关注,在有机合成领域中获得了较多应用.综述了近年来高价有机碘试剂2-碘酰基苯基酸(IBX)在有机合成中的研究及应用,包括IBX在氧化羟基、含氮化合物和含硫化合物,在制备α...     

A new route to α-alkyl-α-fluoromethylenebisphosphonates

A new route to α-alkyl-α-fluoromethylenebisphosphonates, 2 has been developed starting from commercially available tetraethyl fluoromethylenebisphosphonate (1), and alkyl halides using either caesium carbonate in DMF or sodium dimsyl. De-esterification of 2 provided biologically important α-alkyl-α-fluoromethylenebisphosphonic acid, 3, while alkoxide-induced carbon-phosphorus bond cleavage of 2 gave α-fluorophosphonates, 4, which are useful synthons in organic synthesis.     

A Facile and Clean Procedure for Preparation of α-Aminophosphonates via a Rotary Evaporator Equipped with Circulating Water Vacuum Pumps

RE-CWVP (rotary evaporator equipped with a circulating water vacuum pump)–assisted synthesis is reported as an extremely efficient, facile, and clean procedure for the preparation of α-aminophosphonates in organic synthesis and industrial processes. The title α-aminophosphonates are obtained in good to satisfactory yields by the method and characterized by means of IR, ¹H NMR, ³¹P NMR, ¹³C NMR, and mass spectrometry.     

Enzymatic synthesis of optically active α-chloro-δ-hydroxy-β-ketoalkanephosphonates and reactions thereof

A novel and enzymatic approach to α-chloro-δ-hydroxy-β-ketoalkanephosphonates was developed via enantioselective CALB-catalyzed acetylation and CRL-catalyzed hydrolysis. The resultant optically active compounds provide, via Horner-Wadsworth-Emmons (HWE) reaction, chiral α,β-unsaturated ketones that are building block with potential application in organic synthesis.     

One Step Synthesis of α-Substituted α, β-Unsaturated Aldehydes

Abstract

The conversion of carbonyl compounds into cmologated α, β-unsaturated aldehydes (“formylolefination”) is a highly useful transformation in organic synthesis. A large number of methods have been reported for effecting such a chain lengthening. These proceed mainly via silylated intermediates or via phosphorylated reagents. The “phosphonate-strategy” has found widespread use, but leads exclusively to α,β-unsaturated aldehyess, non-substituted in the α-position.     

Access to chiral α-bromo and α-H-substituted tertiary allylic alcohols via copper(I) catalyzed 1,2-addition of Grignard reagents to enones

The catalytic asymmetric synthesis of tertiary alcohols by the addition of organometallic reagents to ketones is of central importance in organic chemistry. The resulting quaternary stereocentres are difficult to prepare selectively by other means despite their widespread occurrence in natural products and pharmaceuticals. Here we report on a new methodology which allows access to both α-bromo-substituted and α-H-substituted allylic tertiary alcohols with excellent yields, and enantioselectivities of up to 98% using the copper(I)-catalysed 1,2-addition of Grignard reagents to enones. As an example, the methodology is applied in the synthesis of a chiral dihydrofuran.     

α-Boryl Carbanions: The Influence of Geminal Heteroatoms in C−C Bond Formation

The wide applications of alpha-boryl carbanions in selective coupling with organohalides, imines/carbonyls and conjugated unsaturated substrates has become an interesting tool for organic synthesis. Strategically, the inclusion of heteroatoms, such as Si, S, N, F, Cl, Br and I in the alpha position opens a new venue towards multifunctionalities in molecular design. Here, a conceptual and practical view on powerful carbanions, containing α-silicoboron, α-thioboron, α-haloboron and α-aminoboron is given, as well as a prespective on their efficient application for selective electrophilic trapping.     

Rapid synthesis and fluorous-phase purification of α-perfluorohexyloligothiophenes

A high-throughput methodology that facilitates the synthesis, purification and characterisation of π-conjugated oligothiophenes has been developed. α-Perfluorohexyltetrathiophene was synthesised by sequential α-bromination and microwave promoted Stille cross-coupling reactions. Each synthetic transformation was followed by a fluorous solid-phase extraction (F-SPE) procedure to isolate the desired α-perfluorohexyloligothiophene. After a single F-SPE, each oligomer gave essentially one peak by GC-MS, which enabled stepwise growth of a tetrathiophene with no additional purification of the intermediate building blocks required. We anticipate that microwave accelerated synthesis in conjunction with fluorous-phase purification of π-conjugated systems will find generic application in the high-throughput parallel-synthesis of novel organic materials for semiconductor applications.