Reactions of α-nitrocinnamic acids esters with indole and its derivatives

Reactions of α-nitrocinnamic acids esters with indole and its derivatives lead to the formation of the products of alkylation at the C₃-reaction center of the heterocycle. The hydrogenation of the adduct of 1-methylindole and α-nitro-β-phenylacrylate on the Raney nickel catalyst afforded indolylaminopropanoate, that was used for the synthesis of ethyl 2-acetylamino-3-(1-methylindol-3-yl)-3-phenylpropanoate, a precursor of the methylated in the indole ring phenyl-substituted tryptophan.     

Copper-catalyzed oxidative coupling of carboxylic acids with formamides for the synthesis of α,β-unsaturated amides

A novel and efficient protocol for the synthesis of α,β-unsaturated amides has been developed using catalytic amount of Cu(OAc)₂ and TBHP as an available oxidant. Oxidative coupling of various unsaturated carboxylic acids with N,N-disubstituted formamides was examined to furnish the desired products in good yields.     

Decomposition of benzenediazonium fluoborate in esters of α,β-unsaturated acids

Summary It was shown that In contrast to the Meerwein-Koelsch reaction, the decomposition of benzenediazonlum fluoborate In esters of ,-unsaturated acids proceeds by a heterolytlc mechanism with the phenyl attacking the -carbon and the carbalkoxyl group of these esters. The reaction with ethyl crotonate gave -methylatropic acid (after hydrolysis) and a small amount of a dibasic acid, C₁₄H₁₆O₄ (or C₁₄H₁₄O₄). With methyl acrylate it gave atropic acid, phenyl acrylate, and a smaller amount of -methyl--phenylglutaric acid. With methyl methacrylate It formed benzylacrylic acid and the product of further conversions of phenyl methacrylate, namely the keto phenol 2-methyl-5-hydroxyindan-1-one.     

A novel synthesis of α, β-unsaturated γ-hydroxy carbonyl compounds from enones with carbon homologation

The alkylation of enone with 1-chloroalkyl phenyl sulfoxide followed by treatment with thiophenolate afforded α-phenylthio-β, γ-unsaturated carbonyl compound, which was oxidized and then hydrolyzed to give α, β-unsaturated γ-hydroxy carbonyl compound in good yield.     

Rhodium-catalyzed asymmetric addition of arylboronic acids to γ-phthalimido-substituted-α,β-unsaturated carboxylic acid esters: an approach to γ-amino acids

Efficient Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to ethyl-γ-phthalimidocrotonate by using bis-sulfoxide ligand affords γ-aminobutyric acid (GABA) derivatives with high enantioselectivities (90-96% ee) under mild conditions. Optically pure (S)-Baclofen and (S)-Rolipram have been prepared successfully through this synthetic route.     

Promiscuous enzyme-catalyzed regioselective Michael addition of purine derivatives to α,β-unsaturated carbonyl compounds in organic solvent

Regioselective Michael addition of purine derivatives to α,β-unsaturated carbonyl compounds could be catalyzed by d-aminoacylase amano (DA) in DMSO. The influence of reaction conditions on the Michael addition, including solvent, temperature, and enzyme concentration was systematically investigated. Then we extended this methodology to six structurally diverse purine derivatives and a variety of α,β-unsaturated carbonyl compounds. 21 Michael adducts were selectively synthesized in moderate to high yields. It is the first report on enzyme-catalyzed Michael addition for the preparation of purine derivatives.     

Reactions of cyclopentanone, γ-butyrolactone,and their derivatives with α-hydroxyethyl radicals

The interaction of cyclopentanone, 2-cyclopentenone, 1,3-cyclopentanedione, 3-methyl-1,2-cyclopentanedione, γ-butyrolactone, 2(5H)-furanone, ascorbic acid, and 5,6-O-isopropylidenyl-2,3-O-dimethylascorbic acid with α-hydroxyethyl radicals (α-HER) generated during the radiolysis of deaerated ethanol has been studied in the continuous irradiation mode. The test compounds, except γ-butyrolactone, oxidize α-HER. 2(5H)-Furanone and 2-cyclopentenone give hydroxyethylation products via the free-radical chain mechanism. In contrast to 2(5H)-furanone and 2-cyclopentenone, ascorbic and 5,6-O-isopropylidenyl-2,3-O-dimethyl-L-ascorbic acids are weaker oxidants for α-HER and attach these radicals at the multiple carbon-carbon bonds.     

Iron-catalyzed, highly regioselective synthesis of α-aryl carboxylic acids from styrene derivatives and CO2

The iron-catalyzed hydrocarboxylation of aryl alkenes has been developed using a highly active bench-stable iron(II) precatalyst to give α-aryl carboxylic acids in excellent yields and with near-perfect regioselectivity. Using just 1 mol % FeCl(2), bis(imino)pyridine 6 (1 mol %), CO(2) (atmospheric pressure), and a hydride source (EtMgBr, 1.2 equiv), a range of sterically and electronically differentiated aryl alkenes were transformed to the corresponding α-aryl carboxylic acids (up to 96% isolated yield). The catalyst was found to be equally active with a loading of 0.1 mol %. Preliminary mechanistic investigations show that an iron-catalyzed hydrometalation is followed by transmetalation and reaction with the electrophile (CO(2)).     

DBU-mediated Ireland-Claisen rearrangement of allyl alk-3-enoates: an efficient synthesis of 2-ethylidene-γ,δ-unsaturated carboxylic acids

Ireland-Claisen rearrangement, triggered by silyl enolization of allylic but-3-enoates 2, has been developed using DBU as the base in the presence of an excess amount of TMSCl under reflux in acetonitrile for a couple of hours. The procedure allows the synthesis of a range of 2-ethylidene-γ,δ-unsaturated carboxylic acids 5 in moderate to high yields. It is further revealed that the rearrangement proceeds equally well with allylic (E)-hexa-3,5-dienoates 10 derived from sorbic acid under similar conditions to provide 2-allyl substituted hexa-2,4-dienoic acids 13.     

Reactions of dibenzylphosphine oxide with α,β-unsaturated nitriles: synthesis of aminophospholene oxides

The reactions of dibenzylphosphine oxide with ,-unsaturated nitriles in the presence of two equivalents of NaH in Bu^tOMe afforded substituted aminophospholene oxides in 20—83% yields. In the presence of bulky substituents at the and positions of unsaturated nitriles, cyclization of the initially formed adducts proceeds with high stereoselectivity to give the single stereoisomer of aminophospholene oxide.     

Reactions of CH-acids with α,β-unsaturated aldehydes in ionic liquids

Metal carbonate-catalyzed reactions of CH-acids (diethyl malonate, ethyl acetoacetate, ethyl cyanoacetate, and ethyl 2-acetyl- and 2-ethoxycarbonyl-5,9-dimethyldeca-4,8-dienoates) with ,-unsaturated aldehydes (acrolein, crotonaldehyde, citral) were studied in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF₆], and in a 1-butyl-3-methylimidazolium bromide ([bmim][Br]) — benzene system. The reactions with acrolein and crotonaldehyde afforded Michael addition products, those with citral resulted in Knoevenagel addition products. Sonication increased the yields of the Michael adducts. The ionic liquid [bmim][PF₆] can be recovered and repeatedly used in the reactions.     

Highly enantioselective γ-amination of α,β-unsaturated acyl chlorides with azodicarboxylates: efficient synthesis of chiral γ-amino acid derivatives

The cinchona alkaloid-catalyzed γ-amination of α,β-unsaturated acyl chlorides with azodicarboxylates to give the corresponding dihydropyridazinones in good yields with high enantioselectivities has been developed. Reductive ring opening of the dihydropyridazinones afforded series of cyclic and acyclic γ-amino acid derivatives in good yields with high enantiopurity.     

One-pot gram-scale synthesis of γ-hydroxybutenolides through catalyst-free annulation of α-amino acids with α-keto acids in water

A one-pot gram-scale synthetic route for the preparation of γ-hydroxybutenolides via catalyst-free annulation of α-amino acids with α-keto acids in water is reported. The method shows many advantages such as readily available starting materials, mild reaction conditions, operational simplicity, acceptable yields, and requiring no extra catalysts or additions. Furthermore, the method is innocuous to the environment, also is valuable to industry.     

Diastereoselective amidoallylation of glyoxylic acid with chiral tert-butanesulfinamide and allylboronic acid pinacol esters: efficient synthesis of optically active γ,δ-unsaturated α-amino acids

A convenient synthesis of δ,γ-unsaturated amino acids has been developed. After a mixture of (R)-tert-butanesulfinamide and glyoxylic acid with molecular sieves in CH₂Cl₂ was stirred for 42 h at room temperature, allylboronic acid pinacol ester was added to the mixture to give (R)-2-((R)-tert-butanesulfinamido)pent-4-enoic acid with high diastereoselectivity. The corresponding reaction of (Z)-crotylboronic acid pinacol ester produced no product; however, that of (E)-crotylboronic acid pinacol ester produced (2R,3S)-2-((R)-tert-butylsulfinamido)-3-methylpent-4-enoic acid with excellent diastereoselectivity.     

Synthesis of functionalized indolizines via copper-catalyzed annulation of 2-alkylazaarenes with α,β-unsaturated carboxylic acids

A novel copper-catalyzed annulation of 2-alkylazaarenes with α,β-unsaturated carboxylic acids has been accomplished. This reaction featuring C-H olefination and decarboxylative amination processes provides a concise access to C-2 arylated indolizines from simple and readily available starting materials.     

Decarboxylative bromination of α,β-unsaturated carboxylic acids via an anodic oxidation

A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation.In this method,ammonium bromide was employed as a bromine source and the reaction features transition-metal-free,short time,and no additional supporting electrolyte.     

Reaction of 2-aminopyridines with α, β-unsaturated acids

The reaction of 2-amino- and 2-amino-5-halopyridines with acrylic, methacrylic, and crotonic acids forms N-(2-pyridyl)- and N-(5-halo-2-pyridyl)--alanines and the betaines 2-amino-1-(2-carboxylatoethyl)pyridinium or 3,4-dihydropyrido[1,2-a]pyrimidin-2-ones, or their homologs.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 80–85, January, 1992.     

Nickel-catalyzed formation of cyclopentenone derivatives via the unique cycloaddition of α,β-unsaturated phenyl esters with alkynes

Oxygen-containing organic compounds, such as ethers, carboxylates, and carbamates, have recently received increasing attention because of their newly discovered applications as electrophiles in cross-coupling reactions via transition metal-catalyzed C-O bond activation. However, no cycloaddition reaction involving their C-O bond activation has been demonstrated thus far. The present study developed a Ni(0)-catalyzed unique [3+2] cycloaddition reaction of α,β-unsaturated phenyl esters with alkynes in (i)PrOH to yield cyclopentenone derivatives.