Synthesis of β-carbolines from aldehydes and ketones via the α-siloxy α,β-unsaturated esters

We report an efficient method for the synthesis of β-carbolines from α-siloxy α,β-unsaturated esters, which are accessible from a variety of aldehydes and ketones.     

A Convenient Synthesis of α-Phenylsclcno-α, β-unsaturated Nitriles via Arsonium Salt

a-Phenylseleno-a,0-unsaturatednitrilesareusefulintermediatesinorganicsynthesisinconsequenceoftheconsiderableversatilityofthetransformationofseleno"andcyano.gooddienophilesandradicophiles'.However,onlyonemethodfortheirpreparationhavebeenreported,'butitsyieldisverylow.Recently,ourinterestinsynthesisandapplicationofa-selenoarsoniumylidesledustoexploita-selenenylationofarsoniumsalt1andconsequentcondensationwitharomaticaldehydesunderweaklybasiccondition.Hereinwewishtoreportanefficientonepotsynthesi…     

Synthesis of 2-oxazolones and α-aminoketones via palladium-catalyzed reaction of β,β-dibromoenamides

β,β-Dibromoenamides show two different interesting reactivities based on the choice of R group under the reaction conditions. On the basis of mechanistic studies, both reactions proceed via an intermolecular Suzuki-Miyaura C-C coupling and an intramolecular C-O coupling.     

Synthesis of β,γ-unsaturated primary amides from α,β-unsaturated acids and investigation of the mechanism

α,β-Unsaturated acids, through their acid chlorides, react with tritylamine in the presence of triethylamine under mild conditions, to afford in high yield and high regioselectivity the corresponding β,γ-unsaturated tritylamides. Detritylation with TFA generates quantitatively β,γ-unsaturated primary amides. An investigation of this deconjugative isomerization was performed.     

Synthesis of α-alkoxyalkyltributyllead compounds via the reaction of tributylplumbyllithium with α-chloroethers,and the conjugate addition of tributylplumbyllithium to enones

α-Alkoxyalkyltributylleads 1 were prepared from the reaction of tributylplumbyllithium with α-chloroethers 2. This procedure is more convenient than the conventional method which involves transmetallation from the corresponding α-alkoxyalkyltrialkyltin. Tributylplumbyllithium was also used for the synthesis of β-oxo-organolead 4.     

Synthesis of chiral organophosphorus compounds by the reaction of dibenzylphosphine oxide with α,β-unsaturated ketones of the terpene series

Dibenzylphosphine oxide readily reacts with ,-unsaturated terpene ketones in aprotic media to form both chiral phosphorus-containing heterocycles and acyclic chiral phosphine oxides.     

Synthesis of unnatural N-glycosyl α-amino acids via Petasis reaction

A convenient and efficient protocol for the synthesis of unnatural N-glycosyl a-amino acids was developed.Condensation of 1,3,4,6-tetra-O-actyl-β-D-glucosamine hydrochloride,alkenyl boronic acid,and glyoxylic acid was achieved in CH_2C1_2 to give the derivatives of 2-(N-glycosyl)aminobut-3-enoic acid which may find applications in glycobiology research and medicinal chemistry.     

Enantioselective synthesis of 3,4-dihydropyran derivatives via organocatalytic Michael reaction of α,β-unsaturated enones

A simple chiral diamine catalyst (1a) was successfully applied in the asymmetric Michael reaction between cyclic dimedone and α,β-unsaturated ketones. Both acyclic enones with aryl or alkyl β-substituents and cyclic enones were tolerated well in the reaction. The desired adducts were obtained in high yields (up to 98%) with excellent enantioselectivities (up to 97% ee). The additives were found to increase the reactivity dramatically. The biologically active 2,4-disubstituted polyhydroquinoline scaffold was conveniently prepared through an ammoniation from the generated 3,4-dihydropyran product.     

Some anomalies in the vibrational spectra of α, β-unsaturated ketones

Summary Some anomalies in the intensities of the bands of the C=C and C=O bonds in the vibrational spectra of , -unsaturated ketones have been explained by a difference in the sequence of the frequencies of the in-phase (_s) and out-of-phase (_as) vibrations of the multiple bonds in their cis (_s<_as) and trans (_s>_as) arrangements.     

A Convenient Synthesis of α,β-unsaturated Nitriles

α,β-unsaturated nitriles were synthesized by the reaction of aldehydes with bromoacetonitrile promoted by tri-n-butylphosphine and zinc.     

Lewis acid-promoted reaction of β,γ-unsaturated α,α-dimethoxy esters with silyl nucleophiles

The Lewis acid-promoted reaction of β,γ-unsaturated α,α-dimethoxy esters, which are easily prepared by the acetalization of β,γ-unsaturated α-keto esters, with silyl nucleophiles is presented. By employing trimethylsilyl enolate and allyltrimethylsilane as nucleophiles, the BF₃-promoted reactions of a series of β,γ-unsaturated α,α-dimethoxy esters bearing aromatic and aliphatic substituents proceeded at the γ-position in an SN2′ manner to furnish γ-substituted α,β-unsaturated α-methoxy esters in good yields with high regioselectivity. In contrast, the reaction using trimethylsilyl cyanide predominantly occurred at the α-position, and the reaction of silyl hydride resulted in a mixture of α- and γ-regioisomers in favor of the γ-substitution products.     

Synthesis of β-substituted tetrahydrofurans by the prins reaction

Mixtures of 3-trif uoroacetoxy- and 3-chloro-4-alkyltetraliydrofurans were synthesized by the reaction of a series of-olefins with formaldehyde in trifuoroacetic acid and trimethylchlorosilane.The characteristics of the mixtures of cis and trans isomers are given, and the n_D ²⁰ values are given for the trans isomers.Bashkir State University, Institute of Fine Organic Synthesis. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 605–608, May, 1995. Original article submitted November 4, 1994; revision submitted May 10, 1995.     

Synthesis of γ,δ-unsaturated quaternary α-alkylamino acids using umpolung reaction and Claisen rearrangement

A new synthesis of γ,δ-unsaturated quaternary α-amino acid derivatives was developed utilizing N-alkylation and Claisen rearrangement of allyl α-iminocarboxylates.     

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.     

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.     

Regioselective synthesis of β-fluoro-α,β-unsaturated ketones by the reaction of β-diketones with DFMBA

The deoxyfluorination reaction of β-diketones with N,N-diethyl-α,α-difluoro-m-methylbenzylamine (DFMBA) gave β-fluoro-α,β-unsaturated ketones in good yields. The reaction proceeded regioselectively, and only one regioisomer was obtained from the unsymmetrical 1-aryl-1,3-diketones. The reaction is applicable to diketones with a trifluoromethyl group, obtaining good yields of 3,4,4,4-tetrafluorobutenones. We used the resulting β-fluoro-α,β-unsaturated ketones for the reaction with lithium dialkyl cuprates.