Alkenoic Acids Research Articles

Vanadium (V) oxide mediated bromolactonization of alkenoic acids

A full account of our recently communicated method for the V2O5 mediated bromolactonization of alkenoic acids is presented. Here we describe the extensive evaluation of the metal oxide catalyst, terminal oxidant, halide source, solvent system, and reaction temperature that resulted in optimal conditions employing 0.05 equiv V2O5, 3 equiv urea-hydrogen peroxide complex (UHP), and 3 equiv of NH4Br in an acetone:H2O (6:1) solvent system at room temperature. Additionally, we have expanded the substrate scope of the reaction with the aim of evaluating the functional group tolerance of the transformation. Further, we present preliminary data of a related halogenation of β-diketones with our optimal conditions. Finally, we probed the role of urea in the transformation.

ChemInform Abstract: De Novo Synthesis of γ,γ‐Disubstituted Butyrolactones Through a Visible Light Photocatalytic Arylation—Lactonization Sequence.

AbstractThe Ru‐catalyzed reaction of alkenoic acids with aryldiazonium salts under the irradiation with white LEDs results in the formation of butyrolactones.

ChemInform Abstract: Bromolactonization of Alkenoic Acids Mediated by V2O5 via Bromide to Bromenium in situ Oxidation.

Abstract An efficient protocol for the bromolactonization of alkenoic acids is presented that obviates the use of molecular bromine or exogenous bromenium sources. Vanadium (V) oxide catalyzes the in situ oxidation of bromide salts to bromenium (Br + ) in a process mediated by urea–hydrogen peroxide complex. Initial mechanistic investigations indicate that the presence of urea does not accelerate the halolactonization reaction.

Mn(OAc)3-mediated arylation–lactonization of alkenoic acids: synthesis of γ,γ-disubstituted butyrolactones

A general method for the synthesis of γ,γ-disubstituted butyrolactones via an arylation–lactonization of alkenoic acids process has been developed.

Mn(OAc)3-mediated phosphonation-lactonization of alkenoic acids: synthesis of phosphono-γ-butyrolactones.

A new, general method for the synthesis of phosphono-γ-butyrolactones has been achieved through Mn(OAc)3-mediated radical oxidative phosphonation and lactonization of alkenoic acids with H-phosphonates and H-phosphine oxide. Mn(OAc)3 can be readily prepared from Mn(OAc)2 in the laboratory. This transformation allows the direct formation of a P-C bond and the construction of a lactone ring in one reaction.

Iridium-catalyzed asymmetric cyclization of alkenoic acids leading to γ-lactones.

Asymmetric cyclization of alkenoic acids was realized by the use of an iridium/chiral bisphosphine catalyst, giving high yields of the corresponding γ-lactones with good enantioselectivity.

Novel Phosphoryloxylactonisation of Pentenoic Acids Mediated by Ammonium Iodide

Using ammonium iodide as a catalyst and m-chloroperbenzoic acid as the oxidant, a novel and efficient procedure has been developed for phosphoryloxylactonisation of alkenoic acids in CH3CN at room temperature, which provides the corresponding phosphoryloxylactones in good yields. In this protocol, it is proposed that ammonium iodide catalyst is first oxidised to hypoiodous acid, which reacts with the alkenoic acid to afford the corresponding iodolactone. Then, the iodolactone is further transformed into a hypervalent iodine intermediate by continuing oxidation, and finally the in situ generated active iodine species reacts with a diaryl phosphate to furnish the phosphoryloxylactone end product.

Rate Accelerations of Bromination Reactions with NaBr and H2O2 via the Addition of Catalytic Quantities of Diaryl Ditellurides

Diaryl ditellurides were oxidized in situ to give aryltellurinic acids, which catalyzed the oxidation of NaBr with H2O2 in buffered aqueous solutions. The aryltellurinic acids were slowly oxidized under the reaction conditions to the corresponding telluronic acids, which did not catalyze oxidation of NaBr with H2O2. Both 4-(methoxyphenyl)tellurinic acid and 4-(methoxyphenyl)telluronic acid were characterized in solution by 125Te NMR and for their effectiveness as catalysts in kinetics studies. The effectiveness of the tellurinic acids as catalysts was very sensitive to electron demand in the intermediates present during the course of the reaction. Electron-withdrawing substituents favor the deprotonated tellurinic acid (tellurinate) in solution, while electron-donating substituents favor the protonated tellurinic acid. Of the nine ditellurides screened for their ability to accelerate the oxidation of NaBr with H2O2, diphenyl ditelluride emerged as the most active. The addition of only 0.20 mol % of this ditelluride (relative to substrate) promoted a 240-fold increase in the rate of oxidation of NaBr with H2O2, as measured by the bromination of 4-pentenoic acid. The “Br+” species prepared in situ were trapped by a series of alkenoic acids and activated aryl compounds.

Bromolactonization of alkenoic acids mediated by V2O5 via bromide to bromenium in situ oxidation

An efficient protocol for the bromolactonization of alkenoic acids is presented that obviates the use of molecular bromine or exogenous bromenium sources. Vanadium (V) oxide catalyzes the in situ oxidation of bromide salts to bromenium (Br+) in a process mediated by urea–hydrogen peroxide complex. Initial mechanistic investigations indicate that the presence of urea does not accelerate the halolactonization reaction.

Fast procedure for the analysis of poly(hydroxyalkanoates) in bacterial cells by off-line pyrolysis/gas-chromatography with flame ionization detector

Poly(hydroxyalkanoates) (PHAs) are polyesters formed by saturated short chain hydroxyacids, among which 3-hydroxybutanoic (HB) and 3-hydroxypentanoic (3-hydroxyvalerate, HV) are the most common monomers of homopolymers (e.g. poly(3-hydroxybutyrate), PHB) and copolymers (e.g. poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), PHB-HC). The most widely used approach for their determination is the polymer methanolysis followed by gas chromatography–mass spectrometry (GC–MS) analysis of the methylated monomers; this procedure generally requires the use of additional reagents (e.g. sulfuric acid) and is performed with harmful chlorinated solvents, such as chloroform. The development of fast routine solventless methods for the quantitative determination of PHAs and their monomeric composition is highly desirable to reduce sample pretreatment, speed up the analysis and decrease overall costs. It has been reported that under thermal treatment (e.g. pyrolysis, Py), PHAs are degraded in high yield (>40%, w/wPHA) into the corresponding 2-alkenoic acid (e.g. crotonic acid from PHB). This work aimed at investigating this reaction for direct analysis of PHAs in bacterial cells. The sample was directly subjected to pyrolysis and trapped pyrolysis products were analyzed by GC–FID. Off-line Py/GC–FID was first optimized on pure polymers with different monomer composition (PHB, PHB-HV, PHB-HC) and then applied to bacterial samples deriving from both mixed microbial cultures or selected strains, containing various types and amounts of PHAs. The Py/GC–FID method provided RSD <15% range, limit of detection of 100μg (1% PHAs in biomass), and results comparable to that of methanolysis (R2=0.9855), but with minimal sample pretreatment.

ChemInform Abstract: Highly Regio‐ and Diastereoselective Synthesis of CF3‐Substituted Lactones via Photoredox‐Catalyzed Carbolactonization of Alkenoic Acids.

AbstractTrifluoromethylative lactonization of both terminal and internal alkenoic acids by photoredox catalysis is developed.

ChemInform Abstract: A Novel One‐Pot Sulfonyloxylactonization of Alkenoic Acids Mediated by Hypervalent Iodine Species Generated in situ from Ammonium Iodide.

AbstractScope and limitations of the novel method are established.

Evaluation of an Upgraded Bio-oil from the Pyrolysis of Rice Husk by Acidic Resin-catalyzed Esterification

A raw bio-oil (RBO) from pyrolysis of rice husk was upgraded by catalytic esterification with methanol over an acidic resin. Both RBO and the upgraded bio-oil (UBO) were analyzed with a Fourier transform infrared spectrometer, pH meter, and an elemental analyzer. They were extracted sequentially with n-hexane, CCl4, CS2, benzene, and CH2Cl2. All of the extracts were analyzed with gas chromatography/mass spectrometer. The results showed that the carboxylic acids (CA) in the RBO were converted to their corresponding methyl esters (MEs), leading to a significant increase in pH value from 2.8 (RBO) to 5.3 (UBO). The total extract yield of UBO is much higher than that of RBO. In total, 20 CAs and 19 MEs were identified. The CAs include two alkenoic acids, a cycloalkanecarboxylic acid, a hydroxyalkanoic acid, a hydroxyalkenoic acid, an oxyalkanoic acid, a methoxyoxyalkanoic acid, an alkanedioic acid, an oxyalkanedioic acid, an aminoalkanoic acid, two furoic acids, three substituted benzoic acids, and five substituted phenylalkanoic acids.

Isothiourea-Mediated Asymmetric Functionalization of 3-Alkenoic Acids

Isothiourea HBTM-2.1 promotes the catalytic asymmetric α-functionalization of 3-alkenoic acids through formal [2 + 2] cycloadditions with N-tosyl aldimines and formal [4 + 2] cycloadditions with either 4-aryltrifluoromethyl enones or N-aryl-N-aroyl diazenes, providing useful synthetic building blocks in good yield and with excellent enantiocontrol (up to >99% ee). Stereodefined products are amenable to further synthetic elaboration through manipulation of the olefinic functionality.

Highly Regio- and Diastereoselective Synthesis of CF3-Substituted Lactones via Photoredox-Catalyzed Carbolactonization of Alkenoic Acids

Trifluoromethylative lactonization of both terminal and internal alkenoic acids by photoredox catalysis has been developed. The use of a Ru photocatalyst and Umemoto's reagent as a CF3 source is key in the present carbolactonization. This is the first example of a highly endo- and diastereoselective synthesis of CF3-substituted five-, six-, and seven-membered ring lactones from internal alkenoic acids.

Catalytic asymmetric aminolactonization of 1,2-disubstituted alkenoic acid esters: efficient construction of aminolactones with an all-carbon quaternary stereo-centre.

Chiral BOX-Cu(OTf)2 catalyzed enantioselective aminolactonization of the tert-butyl ester of alkenoic acids has been developed via in situ aziridination using PhINNs as the nitrene source. It provides exclusively trans-γ- and δ-amino lactones including an additional all-carbon quaternary stereo-centre with up to 98% ee in good to excellent yields.

A Novel One‐Pot Sulfonyloxylactonization of Alkenoic Acids Mediated by Hypervalent Iodine Species Generated in situ from Ammonium Iodide

AbstractA novel and efficient one‐pot procedure was designed for the sulfonyloxylactonization of alkenoic acids by the reaction of alkenoic acids with m‐chloroperbenzoic acid and sulfonic acids in the presence of a catalytic amount of ammonium iodide in a mixture acetonitrile/2,2,2‐trifluoroethanol (4 : 1) at room temperature for 24 h, which provided the corresponding sulfonyloxy lactones in moderate‐to‐good yields.

ChemInform Abstract: Synthesis of γ‐ and δ‐Lactone Natural Products by Employing a trans—cis Isomerization/Lactonization Strategy.

Alkaline hydrolysis of 4-hydroxy- or/and 5-hydroxy-(2E)-alkenoate followed by acid treatment gave the corresponding (2E)-alkenoic acids which were subjected to lactone formation reaction without further purification. The crude acids were treated with 2,4,6-trichlorobenzoyl chloride in pyridine to afford γ-lactone or δ-lactone, respectively, accompanied by trans-cis isomerization. By this procedure, (±)-(4,5)-trans-5-benzyloxy-2-hexen-4-olide (90% overall yield), (S)-5-hydroxy-2-penten-4-olide (86% overall yield), (4S,5R)-5-hydroxy-2-hexen-4-olide (86% overall yield), (4R,5S)-5-hydroxy-2-hexen-4-olide (82% overall yield), (S)-parasorbic acid (58% overall yield) and natural product, (5R,7S)-7-hydroxy-2-octen-5-olide (euscapholide: 20% overall yield) were synthesized.

DFT Study of a 5‐endo‐trig‐Type Cyclization of 3‐Alkenoic Acids by Using Pd–Spiro‐bis(isoxazoline) as Catalyst: Importance of the Rigid Spiro Framework for Both Selectivity and Reactivity

The reaction pathway of an enantioselective 5-endo-trig-type cyclization of 3-alkenoic acids catalyzed by a chiral palladium-spiro-bis(isoxazoline) complex, Pd-SPRIX, has been studied by density functional theory calculations. The most plausible pathway involves intramolecular nucleophilic attack of the carboxylate moiety on the C=C double bond activated by Pd-SPRIX and β-H elimination from the resulting organopalladium intermediate. The enantioselectivity was determined in the cyclization step through the formation of a π-olefin complex, in which one of the two enantiofaces of the olefin moiety was selected. The β-H elimination occurs via a seven-membered cyclic structure in which the acetate ligand plays a key role in lowering the activation barrier of the transition state. In the elimination step, the SPRIX ligand was found to behave as a monodentate ligand due to the hemilability of one of the isoxazoline units thereby facilitating the elimination. Natural population analysis of this pathway showed that the more weakly electron-donating SPRIX ligand, compared with the bis(oxazoline) ligand, BOX, facilitated the formation of the π-olefin complex intermediate, leading to a smaller overall activation energy and a higher reactivity of the Pd-SPRIX catalyst.

ChemInform Abstract: Direct Catalytic anti‐Markovnikov Hydroetherification of Alkenols.

A direct intramolecular anti-Markovnikov hydroetherification reaction of alkenols is described. By employing catalytic quantities of commercially available 9-mesityl-10-methylacridinium perchlorate and 2-phenylmalononitrile as a redox-cycling source of a H-atom, we report the anti-Markovnikov hydroetherification of alkenes with complete regioselectivity. In addition, we present results demonstrating that this novel catalytic system can be applied to the anti-Markovnikov hydrolactonization of alkenoic acids.