Stereoselective Synthesis of (1Z,3E)-2-Ethoxycarbonyl-Substituted 1,3-Dienes via Stille Coupling of (E)-α-Stannyl-α,β-Unsaturated Esters with Alkenyl Halides

Palladium-catalyzed hydrostannylation of alkynyl esters in benzene at room temperature gives stereoselectively (E)-α-stannyl-α,β-unsaturated esters 1 in good yields. (E)-α-Stannyl-α,β-unsaturated esters 1 are difunctional group reagents that undergo Stille coupling reactions with alkenyl halides 2 in the presence of Pd(PPh₃)₄ and CuI co-catalyst to afford stereoselectively (1Z,3E)-2-ethoxycarbonyl-substituted 1,3-dienes 3 in good yields.     

SmI3-Catalyzed Addition of Amines to α,β-Unsaturated N-Acylbenzotriazoles

The addition of amines to α,β-unsaturated N-acylbenzotriazoles could be catalyzed by samarium triiodide (SmI₃) at ambient temperature. α,β-Unsaturated aliphatic N-acylbenzotriazoles afforded bis-addition products (β-amino amides), whereas N-cinnamoylbenzotriazoles gave acylated products (cinnamoylamides) exclusively.     

Nmp-based ionic liquids: Recyclable catalysts for both hetero-Michael addition and Knoevenagel condensation in water

A series of novel N-methyl piperidine (Nmp)-based ionic liquids with 1,2-propanediol group are synthesized and used as catalysts for both hetero-Michael addition of α,β-unsaturated amides and Knoevenagel condensation at room temperature in water; and all the examined substrates could be transformed into corresponding products in good to excellent yields. Meanwhile IL-catalyzed hetero-Michael addition of α,β-unsaturated amides in water has not been reported in the previous literatures. Additionally, the catalyst is recyclable for the two reactions. This finding provides a green catalyst for both hetero-Michael addition of α,β-unsaturated amides and Knoevenagel condensation in water.     

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

A series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR, IR spectroscopy and HRMS.     

Aza-Michael Addition of Amines to α,β-Unsaturated Compounds Using Molecular Iodine as Catalyst

Aza-Michael adducts are obtained in very good yields by the conjugate addition of aliphatic amines to α,β-unsaturated compounds using molecular iodine as catalyst in dichloromethane at room temperature. Aromatic amines were found to be reactive under reflux in toluene.     

Polymer-Assisted Solution-Phase Synthesis Under Combined Ultrasound and Microwave Irradiation: Preparation of α,β-Unsaturated Esters and Carboxylic Acids,Key Intermediates of Novel Sigma Ligands

The optimal conditions to prepare α,β-unsaturated methyl esters via Wittig reaction combining polymer-assisted solution-phase synthesis (PASPS) methodology and simultaneous ultrasound and microwave irradiation were established. The effects of temperature, solvent, and irradiation time were discussed. Results clearly indicated the superiority of combined ultrasound and microwave-assisted procedure over microwave-assisted methodology. Moreover, an efficient PASPS procedure to prepare α,β-unsaturated carboxylic acids via tandem Wittig olefination and hydrolysis reaction was developed under combined ultrasound and microwave irradiation. Generally, a good conversion of aldehydes to acids was observed. The optimized protocols allowed us to quickly prepare a small collection of either α,β-unsaturated esters or carboxylic acids, key intermediates for the drug-discovery process of new sigma ligands.     

One-Pot Approach to the Conversion of Alcohols into α-Iodo-α,β-unsaturated Esters

(Carboethoxymethylene)triphenylphosphorane 1 can undergo the tandem reaction of iodination–oxidation–Wittig reaction with alcohol in the presence of N-iodosuccinimide (NIS) and manganese dioxide. The reaction constitutes a stereoselective one-pot procedure for the preparation of Z-configured α-iodo-α,β-unsaturated esters in good to excellent yield.     

Aqueous-Phase Synthesis of α-Hydroxyphosphonates Catalyzed by β-Cyclodextrin

α-Hydroxyphosphonates were synthesized from aromatic/heteroaromatic aldehydes with triethyl phosphite in the presence of β-cyclodextrin in an aqueous medium. The β-cyclodextrin can be recovered and reused without loss of catalytic activity.     

Natural α-Amino Acid L-Lysine–Catalyzed Knoevenagel Condensations of α,β-Unsaturated Aldehydes and 1,3-Dicarbonyl Compounds

Knoevenagel condensations of α,β-unsaturated aldehydes and 1,3-dicarbonyl compounds were catalyzed by primary natural amino acid L-lysine. The reactions were carried out at room temperature in dimethylsulfoxide. It provides a facile entry to a wide variety of α,β,γ,δ-unsaturated dicarbonyl compounds.

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Highly Efficient Michael Addition Reaction of Amines Catalyzed by Silica-Supported Aluminum Chloride

Aliphatic and aromatic amines undergo smooth nucleophilic addition to α,β-unsaturated compounds in the presence of a catalytic amount of silica-supported aluminum chloride at 60 °C and under solvent-free conditions to produce the corresponding β-amino compounds in excellent yields. This method is simple and convenient and works efficiently under mild conditions. This catalyst can used again without losing its activity three times.     

Asymmetric Reformatsky Reaction of Aldehydes Catalyzed by Novel β-Amino Alcohols and Zinc Complexes

A series of β-amino alcohols derived from (1R, 2S)-2-amino-1,2-diphenylethanol and substituted salicylaldehydes as novel chiral tridentate ligands has been applied to an asymmetric Reformatsky reaction of aldehydes with ethyl iodoacetate in the presence of ZnMe₂. This novel catalytic system produced the desired β-hydroxyl esters with moderate to good enantioselectivities (up to 81% ee) and yields for many aldehydes, including aromatic, heteroaromatic, conjugated, and aliphatic aldehydes.     

Direct access to α,α′-diarylated ketones through N-heterocyclic carbene-catalyzed 1,6-addition of aromatic aldehydes to para-quinone methides

N-Heterocyclic carbene-catalyzed 1,6-addition of aromatic aldehydes to para-quinone methides has been developed. This method could efficiently furnish α,α′-diarylated ketones with good to high yields, which contain various functional groups.     

Synthesis and Fluorescence Properties of α,α′-Bis(substituted-benzylidene)cycloalkanones Catalyzed by 1-Methyl-3(2-(sulfooxy)ethyl)-1H-imidazol-3-ium Chloride

α,α′-Bis(substituted-benzylidene)cycloalkanones were synthesized via a solvent-free cross-aldol condensation of aromatic aldehydes with cycloalkanones in the presence of a catalytic amount 1-methyl-3(2-(sulfooxy)ethyl)-1H-imidazol-3-ium chloride at room temperature with excellent yields. The screening for optical properties indicated that the size of cycloalkanone has an influence on the fluorescence emission of products. Products coming from cyclohexanone have stronger fluorescence emission than those from cyclopentanone.     

Efficient Aziridination of α,β-Unsaturated Ketones with O-(2,4-Dinitrophenyl)-hydroxylamine

The aziridination of α,β-unsaturated ketones with O-(2,4-dinitrophenyl)-hydroxylamine and tertiary amine was developed. trans-Aziridines were obtained exclusively in good yields. The reaction is proposed to occur via an aminimide intermediate.     

Selective Bromination of Dehydroacetic Acid with N-Bromosuccinimide

Bromination of dehydroacetic acid has been carried out with N-bromosuccinimide under various conditions. The reactions led to selective bromination, thereby offering efficient synthesis of 3β-bromodehydroacetic acid (3), 3β,5-dibromodehydroacetic acid (4), 3β,3β-dibromodehydroacetic acid (5), and 3β,3β,5-tribromodehydroacetic acid (6).     

The Reaction of Electron-Deficient Cyclopropane Derivatives with Aromatic Amines

Abstract

N-Aryl-trans,trans-α-carboxyl-β-benzoyl-γ-aryl-γ-butyrolactams were synthesized in high yields with high stereoselectivity by the reaction of electron-deficient cyclopropane derivatives, cis-1-benzoyl-2-aryl-6,6-dimethyl-5,7-dioxo-spiro-[2 (a) Zhang , J. ; Blazecka , P. G. ; Davidson , J. G. First direct reductive amination of mucochloric acid: A simple and efficient method for preparing highly functionalized α,β-unsaturated γ-butyrolactams . Org. Lett. 2003 , 5 , 553 – 556 ; (b) Sarma, K. D.; Zhang, J.; Curran, T. T. Novel synthons from mucochloric acid: The first use of α,β-dichloro-γ-butenolides and γ-butyrolactams for direct vinylogous aldol addition. J. Org. Chem. 2007, 72, 3311–3318 . [Google Scholar] 5 (a) Chen , Y. L. ; Ding , W. Y. A simple approach to highly stereoselective synthesis of β γ-trans-γ-butyrolactones . Chem. J. Chin. Univ. 1998 , 19 , 1614 – 1616 ; (b) Chen, Y. L.; Ding, W. Y.; Cao, W. G.; Lu, C. Stereoselective synthesis of N-aryl-trans,trans-α-carboxyl-β-methoxycarbonyl-γ-aryl-γ-butyrolactones. Synth. Commun. 2002, 32, 1953–1960.  [Google Scholar]]-4,8-octadiones, with aromatic amines. The reaction mechanism was proposed.     

Brønsted Acid–Catalyzed Meyer–Schuster Rearrangement for the Synthesis of α,β-Unsaturated Carbonyl Compounds

An efficient and simple protocol for the Meyer–Schuster rearrangement of propargyl alcohols into α,β-unsaturated carbonyl compounds has been developed using catalytic amounts of p-toluenesulfonic acid in 1,2-dichloroethane.     

Sustainable Synthesis of the Naturally Hypolipidemic Agent α-Asarone

A short and practical preparation of α-asarone was developed using the inexpensive methylisoeugenol as a starting material. The utilization of a sequence of tribromination, debromination, and copper-mediated aromatic substitution enabled the stereoselective formation of only the E-isomer of α-asarone in good yield.     

Facile synthesis of novel α-methylene-pyrazole-carboxylate substituted imines and trans-β-lactams: Versatile synthons for diverse heterocyclic molecules

A simple, facile, and high yielding stereoselective approach for the integration of α-methylene-pyrazole-carboxylates at the β-lactam nucleus is described. These monocyclic β-lactams have been synthesized by treatment of 2-phenoxy/benzylthio/phenylthio ethanoic acids or acetoxyacetyl chloride/phthalimidoacetyl chloride 5a–e with novel α-methylene-pyrazole-carboxylate imines 4a–c using Et₃N and POCl₃ in refluxing toluene. All of the newly synthesized α-methylene-pyrazole carboxylate imines 4a–c and their β-lactam derivatives 6a–h have been fully characterized by spectroscopic techniques such as FTIR, NMR (¹H, ¹³C, and ¹³C DEPT-135), 2D-NMR (COSY and HSQC), and elemental analyses (CHN). The cycloaddition reaction was found to be highly stereoselective leading to the exclusive formation of trans-β-lactams 6a–h and trans configuration was assigned with respect to coupling constant values of C3-H and C4-H. The novel β-lactams 6a–h bearing α-methylene-pyrazole-carboxylate ring system will serve as useful synthons for highly functionalized acids, acetohydrazides/pyrazolones, alcohols, pyrazole carboxamides, peptides, and promising biologically active agents.     

Synthesis of Enantiomerically Enriched α-Bromonitriles from Amino Acids

Two methods were investigated for the preparation of six chiral α-bromonitriles with different optic purities. The nitrous deamination of amino acids gives α-bromoacids, which react with chlorosulfonyl isocyanate followed by triethylamine to afford α-bromonitriles with moderate enantiomeric excess. However, the dehydration of corresponding α-bromoamids using thionyl chloride gives α-bromonitriles with good enantiomeric excess up to 94%. The use of phosphoryl chloride instead of thionyl chloride results in more than 30% racemization as determined by high-performance liquid chromatograpic analysis.