Bromination of polyfluorinated α,β-enones

Polyfluoroalkyl-,-enones readily add Br₂ to give ,ß-dibromoketones. The latter are readily and regioselectively dehydrobrominated to -bromo-,-enones on treatment with K₂CO₃ or NEt₃ Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2134–2136, December, 1993.     

Asymmetric synthesis of β′-amino-α,β-enones via addition of α,β-unsaturated ketone-derived enolates to chiral N-phosphonyl imines

Efficient asymmetric Mannich addition reactions between α,β-unsaturated ketone derived enolates and N-phosphonyl imines were reported. These reactions could proceed smoothly for a variety of imine substrates with good (up to 96%) chemical yields and excellent diastereoselectivities (up to 98:2 dr). The method reported in this work provides an easy access to chiral β′-amino-α,β-enones.     

Three-component reactions of phosphorus ylides,thiophenols, and acetyl chloride for the synthesis of (β-thioacrylates)

The facile synthesis of β-thioacrylates has been realized via direct three-component reactions of thiophenols, Wittig reagents, and acetyl chloride. Under transition metal-free conditions, a class of β-thioacrylates have been synthesized with fair to excellent yields via cascade C=C double bond and C(sp² Kano, T.; Shirozu, F.; Akakura, M.; Maruoka, K. J. Am. Chem. Soc. 2012, 134, 16068-16073.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar])-S bond formation.     

Synthesis of pyrazolines by the reactions ofα,β-enones with diazomethane and hydrazines (review)

The first representatives of pyrazolines were synthesized in the last century. These nitrogen-containing heterocyclic compounds became important in the development of different bioactive substances. For this reason, various procedures have been worked out for their synthesis. In the present article we summarize those synthetic methods providing 1- or 2-pyrazolines by the reactions of ,-unsaturated ketones with diazomethane or hydrazine derivatives.Department of Organic Chemistry, Kossuth Lajos University, Egyetem ter I, H 4010 Debrecen, Hungary. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 747–759, June, 1997.     

Stereoisomerism ofβ-polyfluoroalkyl-α,β-enones

-Polyfluoroalkyl-,-enones formed in the E,Z form are converted by the action of atmospheric oxygen into a 937 mixture of E,Z and Z,E isomers in the dark and 6040 mixture of these isomers in the light. The Z isomer of 1-phenyl-4,4, 4-trifluoro-2-buten-1-one was isolated preparatively for the first time and its E conformation relative to the C-C bond was established. The Z,E isomer spontaneously transforms into the indicated equilibrium mixtures.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1685–1689, July, 1991.     

Highly enantioselective Mannich reactions with α-aryl silyl ketene acetals and imines

Mannich reactions with chiral silicon Lewis acid activated acylhydrazones and α-aryl silyl ketene acetals and α-aryl,α-alkyl silyl ketene imines proceed efficiently and with good to excellent levels of both diastereoselectivity and enantioselectivity. The reactions provide access to α-aryl,β-hydrazido esters and α-aryl,α-alkyl,β-hydrazido nitriles, which are valuable analogs of β-amino acids.     

Three-component synthesis of polysubstituted pyrroles from α-diazoketones, nitroalkenes, and amines

Polysubstituted pyrroles are regiospecifically synthesized via the copper-catalyzed three-component reaction of α-diazoketones, nitroalkenes, and amines under aerobic conditions. The cascade process involves an N-H insertion of carbene, a copper-catalyzed oxidative dehydrogenation of amine, and a [3 + 2] cycloaddition of azomethine ylide.     

Green, efficient and practical Michael addition of arylamines to α,β-unsaturated ketones

The aza-Michael addition of aromatic amines to α,β-unsaturated ketones was carried out effectively at room temperature in good to excellent yields without any catalyst or solvent. It was significant that part of adducts could be collected in almost quantitative yield without column chromatography. This procedure offered a green, efficient, and practical approach for the synthesis of β-amino ketones.     

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.     

Synthesis of Substituted Pyrroles via Ultrasound Assisted Three-component Coupling Reaction of Amines, α,β-Unsaturated Aldehydes and Nitroalkanes

IntroductionPyrrolesareimportantsynthetictargetssincetheyareappliedasprecursorstomanyusefulclassesoforganiccom poundssuchasporphyrinsandalkloids.1Severalsubstitutedpyrroleshavepotentialapplicationasfungicidsandbacteri cidesandasactivecomponentsofnonsteroidalanti inflamma torydrugsinhibitinghumancyclooxygenase.2 ,3Inaddition ,aminoacidssuchasprolineandhydroxyprolinealsocontainthehydrogenatedpyrroleringthatisapyrrolidineframework .Althoughthereareanumberofpotentiallyusefulmethodsforthesynthesiso…     

The efficient consecutive β-carboxylation and α-alkylation of cyclic α,β-enones; a new route to sarkomycin

Sequential one-pot introduction of a carboxy group equivalent and an alkyl group at the respective β- and α-positions of cyclic enones has been achieved through a 1,4-addition reaction of [methoxy(phenylthio)(trimethylsilyl)methyl] lithium followed by direct trapping of the resulting enolate with alkyl halides. The present method proved to be applicable to a simple synthesis of sarkomycin.     

Asymmetric Michael addition of silyl nitronates to cyclic α,β-unsaturated ketones catalyzed by chiral quaternary ammonium bifluorides: isolation and selective functionalization of enol silyl ethers of optically active γ-nitro ketones

Highly enantioselective Michael addition of silyl nitronates to cyclic α,β-unsaturated ketones has been accomplished by the utilization of N-spiro C₂-symmetric chiral quaternary ammonium bifluoride 1 as an efficient catalyst, offering a new route to the enol silyl ethers of optically active γ-nitro ketones. The synthetic utility of this transformation has been demonstrated by the diastereoselective derivatizations of the optically active enol silyl ethers to the corresponding α-substituted cyclic ketones having three consecutive stereochemically defined stereocenters.     

Synthesis of β-Fluoroalkyl-β,β-dimethoxy Ketones and β-Fluoroalkyl-β-methoxy-α,β-enones

α-Bromo-β-fluoroalkyl-α,β-enones react with sodium methoxide in methanol to give the corresponding β-fluoroalkyl-β,β-dimethoxy ketones which eliminate methanol molecule to produce a mixture of E/Z-isomeric β-fluoroalkyl-β-methoxyvinyl ketones, the Z isomer prevailing.     

Studies on the reactions of silyl enol ether with perfluoroorganic compounds——Ⅲ.Synthesis of perfluoroalkylated α,β-unsaturated aldehydes and their derivatives

Per-and poly-fluoroalkylated α,β-unsaturated alkenals were synthesized by the reaction of silylenol ether of alkanals with per-and poly-fluoroalkyl iodide initiated by Na_2S_2_O4 conveniently inhigh yield.Their corresponding alkenol and 2,4-dinitrophenylhydrazone were also synthesized.     

Features and applications of reactions of α,β-unsaturated N-acylbenzotriazoles with amino compounds

Promoted by triethylamine, α,β-unsaturated N-acylbenzotriazoles reacted with amino compounds in a variety of ways. Thus, N-cinnamoylbenzotriazoles reacting with aromatic amines afforded novel addition products β-benzotriazolyl amides 3, which might be normally formed from the alternative but unknown 1,4-addition of benzotriazole to N-cinnamoylamides. The type 3 compounds could also result from the reaction between N-crotonoylbenzotriazole and aliphatic amines. However, normal 1,4-addition could occur between α,β-unsaturated aliphatic N-acylbenzotriazoles and aromatic amines, leading to β-amino N-acylbenzotriazoles 4 in good yields. In addition, exclusive 1,2-addition of aliphatic amines to N-cinnamoylbenzotriazoles gave excellent yields of cinnamides 5. Accordingly, three possible routes were proposed to rationalize the formation of compounds 3-5. Finally, with o-phenylenediamine and o-aminothiophenol as the substrates, the 1,4- and 1,2-addition to α,β-unsaturated N-acylbenzotriazoles could take place concurrently and the corresponding heterocycles 1,5-benzodiazepine-2-one and 1,5-benzothiazepine-4-one were constructed, respectively.     

New synthetic methods for α,β -unsaturated ketones,aldehydes, esters and lactones by the palladium-catalyzed reactions of silyl enol ethers,ketene silyl acetals,and enol acetates with allyl carbonates

Silyl enol ethers and ketene silyl acetals derived from ketones, aldehydes, esters and lactones are converted into α,β-unsaturated ketones, aldehydes, esters and lactones by treatment with allyl carbonates in high yields using the palladium—bis(diphenylphosphino)ethane (dppe) complex as catalyst. Phosphine-free palladium catalyst instead of the palladium—phosphine complex gives a higher selectivity for the preparation of cyclopentenone, cyclooctenone, dienones, α,β-unsaturated esters and lactones. As a solvent, the use of nitriles such as acetonitrile is essential. In other solvents, allylation takes place. Enol acetates derived from ketones are converted into α,β-unsaturated ketones by reaction with allyl carbonate in acetonitrile using the palladium complex and tributyltin methoxide as bimetallic catalysts.     

A diastereo- and enantioselective Michael addition of chiral amide enolates to α, β-unsaturated esters a stereoelective synthesis of (+)-dehydroiridodiol and (−)-isodehydroiridodiol

(+)-Dehydroiridodiol and (−)-isodehydroiridodiol were synthesized stereoselectively using the diastereo- and enantioselective Michael addition of chiral amide enolates to α, β-unsaturated esters.