Polyenolates of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Unsaturated α-Amino Acids and β-Hydrazing Acids

Regioselective reaction of lithium diene-and triene-diolates 1 and 2 with O-diphenylphosphinyl hydroxylamine affords unsaturated α-amino acids 3 and 4. Addition to DEAD leads selectively to γ-hydrazino unsaturated acids 5 and 6.     

MgBr2‐Mediated Ionic Diels–Alder Reaction of Acetals of α,β‐Unsaturated Aldehydes and Ketones with 1,3‐Dienes

A facile, mild, and efficient methodology for the ionic Diels–Alder reaction of acetals of α,β‐unsaturated ketones and aldehydes as dienophiles with various 1,3‐dienes employing MgBr₂ as the Lewis acid catalyst to furnish corresponding Diels–Alder adducts at ambient temperature is described.     

Selective Esterification of Aliphatic Carboxylic Acids in the Presence of Aromatic Carboxylic Acids Over Monoammonium Salt of 12‐Tungstophosphoric Acid

Monoammonium salt of 12‐tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀] was found to be a practical and useful heterogeneous catalyst for an efficient and selective esterification of aliphatic carboxylic acids with alcohols in the presence of aromatic carboxylic acids. The heteropoly acid–based heterogeneous catalyst has the advantages of a simple workup procedure, water insolubility, and good activity.     

Acidic Ionic Liquid–Catalyzed Highly Efficient Reaction of Indoles to α,β‐Unsaturated Ketones

A novel method for the Michael reaction of indoles to α,β‐unsaturated ketones catalyzed by acidic ionic liquid is reported. We obtained the corresponding products in excellent yields in the presence of [hmim]HSO₄. Development of this method has resulted in a new protocol for the synthesis of β‐indolylketones.     

Zirconium(IV) Chloride–Mediated Chemoselective Conjugate Addition of Aliphatic Amines to α,β‐Ethylenic Compounds

Zirconium chloride efficiently catalyzes the conjugate addition of a variety of aliphatic amines to α,β‐unsaturated ester, nitriles, and ketones to give the corresponding β‐amino derivatives in excellent yields under mild reaction conditions. Aromatic amines do not participate in this transformation.     

One‐Pot Wittig Reactions in Aqueous Media: A Rapid and Environmentally Benign Synthesis of α,β‐Unsaturated Carboxylic Esters and Nitriles

One‐pot Wittig reactions of ethyl bromoacetate and bromoacetonitrile with aldehydes in the presence of PPh₃ and LiOH in water were investigated. Most of the olefination reactions completed within 5–120 min in refluxing water containing 1.2 M LiCl to afford the olefin products in 71–97% yields with 100:0–55:45 ratios of E:Z isomers.     

Antimony Trichloride–Catalyzed Michael Addition of Indoles to the α,β‐Unsaturated Ketones

Indoles undergo conjugate addition with α,β‐unsaturated ketones in the presence of a catalytic amount of antimony trichloride under refluxing condition to afford the corresponding Michael adduct in excellent yields. The substitution on the indole ring occurred exclusively at 3‐position without a trace of any N‐alkylated products.     

Synthesis and Hydrophosphorylation of π-Complexes of Esters of Unsaturated Carboxylic Acids with Chromium Subgroup Metals

Photochemical and thermochemical activation were used to prepare new -complexes of chromium, molybdenum and tungsten containing ²- and ⁴-coordinated methyl acrylate, methyl cynnamate, and dimethyl fumarate molecules. Geometric, electronic, and energetic parameters of the coordinated ester molecules were found and factors governing ²- and ⁴-coordination of the oxodiene system were revealed by nonempirical calculations. Monocarboxylic acid esters incorporated in the -complexes react with dialkyl hydrogen phosphites to give dialkyl acyl phosphites coordinated with the metal center and susceptible to oxidation the corresponding phosphates. In this case, the phosphorylation involves the OH-tautomer of dialkyl hydrogen phosphite. Coordinated dimethyl fumarate undergoes phosphorylation by two concurrent pathways, viz. transesterification or Pudovik reaction. In the latter case, fragmentation of the organometallic compound takes place.     

A Protocol for Accessing the β-Azidation of α,β-Unsaturated Carboxylic Acids

This contribution reports the preparation and use of a new immobilized catalyst, PS-DABCOF (9), which has been specifically designed to access for the first time the efficient β-azidation of α,β-unsaturated carboxylic acids.     

One-Pot,Three-Component Coupling Reaction: Catalyst-Free Green Synthesis of Novel N-Heteroaryl α-Naphthylglycines

A series of novel N-heteroaryl α-arylglycines containing naphthol rings has been prepared by one-pot, three-component condensation reaction of glyoxalic acid, heteroaryl amines and naphthols in water at ambient temperature and under reflux conditions in moderate to high yields. The promising advantages such as removal of organic solvent, no need to catalyst, simplicity of the reaction procedure and easy product separation will be discussed in this article.     

Study of the Three-component Reaction of α-Nitrocarbonyl Compounds, Aromatic Aldehydes, and Cyanothioacetamide

The reaction of benzaldehyde, -nitro ketone, and cyanothioacetamide in the presence of morpholine has given the novel 3,4-trans-2-R-5-cyano-2-hydroxy-3-nitro-4-phenyl-1,2,3,4-tetrahydropyridine-6-thiolates. It was found that the reaction occurs via the formation of 1-amino-2-cyano-4-nitro-5-oxo-3-phenyl-1,2-pentene-1-thiolate. In the case of -nitroacetophenone, 3,4-trans-4,5-trans-5-cyano-2-hydroxy-3-nitro-2,4-diphenylhexahydropyridine-6(1H)-thione was also obtained. The use of -nitroesters in place of the nitro ketones in the reaction leads to morpholinium 2-aryl-1-carbethoxy-3-cyano-1-nitro-3-thiocarbamoylpropyl-1-ates as the single product.     

Enantioselective 1,4-Addition Reaction of α,β-Unsaturated Carboxylic Acids with Cycloalkanones Using Cooperative Chiral Amine–Boronic Acid Catalysts

An enantioselective 1,4-addition of α,β-unsaturated carboxylic acids with cycloalkanones has been developed by using chiral amine–boronic acid cooperative catalysts. In the presence of a chiral amine and boronic acid, cycloalkanones and carboxylic acids are activated as chiral enamines and mixed anhydrides, respectively. The corresponding 1,4-adducts are obtained in high yield with high enantioselectivity. Furthermore, subsequent oxylactonization of the 1,4-adducts gives spirolactones with high diastereoselectivity.     

Beyond Kolbe and Hofer–Moest: Electrochemical Synthesis of Carboxylic Anhydrides from Carboxylic Acids

Herein we report a conceptually new non-decarboxylative electrolysis of carboxylic acids to obtain their corresponding anhydrides as highly valuable reagents in organic synthesis. All carbon atoms of the starting material are preserved in the product in an overall redox-neutral reaction. In a broad substrate scope of carboxylic acids the anhydrides are generated with high selectivity, which demonstrates the versatility of the developed method. Beneficially, no dehydrating reagents are required in comparison to conventional methods and the synthesis is based on uncritical starting materials using graphite and stainless steel as very inexpensive and eco-friendly electrode materials.     

Mechanistic Study of Catalysis in the Mizoroki–Heck Reaction with Anhydrides of Aromatic Acids

A kinetic study of reaction of alkene arylation by anhydrides of aromatic acids (modified Mizoroki–Heck reaction) was carried out using differential selectivity as the main measured parameter. The results obtained under conditions of competition between a pair of alkenes or a pair of aromatic anhydrides point to the occurrence of the reaction via a homogeneous mechanism of catalysis analogously to a conventional variant of reaction with aryl halides as arylating reagents. The hypothesis that the active catalyst is homogeneous agrees with the results of kinetic studies of processes of catalyst formation and deactivation.     

A Convenient Procedure for the Conversion of Carboxylic Acids to α-Bromo Thiolesters

Carboxylic acids can be conveniently transformed to the corresponding α-bromo thiolesters by a one-pot procedure involving Hell-Volhard-Zelinsky reaction and trapping the α-bromo acyl bromide intermediate with mercaptans.     

A Novel Approach to Synthesis of α，β－Unsaturated Ketones

A new approach to the synthesis of α，β-unsaturated ketones from 1,2,3-trimethyl benzimidazolium salt via the condensation reaction with aldehydes followed by the addition reaction of Grignard reagents with quaternary C=N bond was provided.     

Multicomponent Reaction in Ionic Liquid： A Novel and Green Synthesis of 1, 4-Dihydropyridine Derivatives

1, 4-Dihydropyridine (DHP) heterocyclic ring is a common feature of various bioactivecompounds such as vasodilator, bronchodilator and antiatherosclerotic, antitumor, andantidiabetic agents1. Due to their important pharmacological activities, many methods…     

Efficient CuCl-Catalyzed Selective and Direct Oxidation of β- and γ-Substituted Aliphatic Primary Alcohols to Carboxylic Acids

A new procedure for the selective and direct oxidation of aliphatic primary alcohols having substitution at β- and γ-positions to corresponding carboxylic acids was developed using a catalytic amount of ligand and additive-free CuCl with anhydrous ^t BuOOH in acetonitrile solvent under very mild reaction conditions. This procedure is very simple and mild and works efficiently without any additives at room temperature.     

Synthesis and Characterization of Photosensitive Phosphorus Based Polymers Containing α,β‐Unsaturated Ketones in the Main Chain

1,3‐Bis(4‐hydroxyphenyl)propenone (BHPP) and 3‐(4‐hydroxy‐3‐methoxy phenyl)‐1‐(4‐hydroxyphenyl)propenone (HMPHPP) were used as monomers for preparing photosensitive phosphorus containing polyesters. The photosensitive monomers BHPP and HMPHPP were prepared respectively by refluxing 4‐hydroxybenzaldehyde and 3‐methoxy‐4‐hydroxybenzaldehyde with 4‐hydroxy acetophenone. The polyesters were synthesized by interfacial polycondensation of photosensitive diols with N‐phenylphosphoramidic dichloride using hexadecyltrimethyl ammonium bromide (HDTMAB) as phase‐transfer catalyst. Copolymers were also prepared by incorporating terephthaloyl chloride in the polymer backbone. The synthesized monomers and polymers were characterized by UV, FT‐IR and ¹H, ¹³C and ³¹P‐NMR spectroscopic techniques. The resulting polymers had inherent viscosities in the range of 0.15–0.51 dL/g and showed good solubility in polar organic solvents. The thermal properties of the polymers were studied by thermogravimetric analysis and differential scanning calorimetry under nitrogen atmosphere. The TGA data revealed that the 10% weight loss occurs at 275–320°C and all the synthesized polymers showed high char residues. DSC studies indicate that these polymers possess T_g in the range of 48 to 64°C. The photosensitive property of the polymers in film and solution state was investigated by ultraviolet spectroscopy. The effect of incorporation of terephthaloyl unit on photocrosslinking and thermal properties of the polymers was also studied.     

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.