Balance between allylic C-H activation and cyclopropanation in the reactions of donor/acceptor-substituted rhodium carbenoids with trans-alkenes

Rhodium(II)-catalyzed reactions of aryldiazoacetates with (E)-aryl-substituted alkenes generate C-H insertion products and/or cyclopropanes. The product distribution is influenced by the nature of the donor group on the carbenoid, the structure of the (E)-aryl-substituted alkenes, and the rhodium catalyst.     

Lipase-catalyzed kinetic resolution of 3-butyn-2-ol

Optically active 3-butyn-2-ol, an important building block, was synthesized successfully using lipase-catalyzed kinetic resolution. Starting from the thus obtained 3-butyn-2-ol, several 4-aryl-substituted compounds were synthesized enantioselectively.     

微波辐射下2-芳基取代苯并噁唑的合成

邻氨基酚和芳香羧酸在微波辐射条件下缩合,合成了4种2-芳基取代苯并噁唑化合物。优化反应条件为：多聚磷酸为催化剂,辐射功率500W,辐射时间4min。     

Enantioselective Michael addition of 3-aryl-substituted oxindoles to methyl vinyl ketone catalyzed by a binaphthyl-modified bifunctional organocatalyst

The enantioselective conjugate addition reaction of 3-aryl-substituted oxindoles with methyl vinyl ketone promoted by binaphthyl-modified bifunctional organocatalysts was investigated. The corresponding Michael adducts, containing a quaternary center at the C3-position of the oxindoles, were generally obtained in high yields with excellent enantioselectivities (up to 91% ee).     

A Simple Route to New N(3)-Substituted 5-Aryl-2-(dialkylamino)-1,3-oxazolium Salts and N(1)-Substituted 4-Aryl-2-(dialkylamino)-1H-imidazoles

In the reaction of N,N-dialkyl-dichloromethaniminium chlorides 11 with 2-aminoacetophenones 12 , a general and simple route to heretofore unknown 5-aryl-substituted 2-(dialkylamino)-1,3-oxazolium salts 13 and 5-aryl-substituted 2-(dialkylamino)oxazoles 14 was found. From the 2-(dialkylamino)-1,3-oxazoles 14 , the corresponding oxazolium salts 13 were obtained after alkylation with (MeO)₂SO₂. The new oxazolium salts 13 were converted to 1-substituted 4-aryl-2-(dialkylamino)-1H-imidazoles 9 by treatment with NH₄OAc. The possible use of these 1H-imidazoles as dye educts was explored. Analytical data, as well as AM1 calculations, reveal some remarkable differences between the structures of the neutral imidazoles 9 and their positively charged oxazolium precursors 13 .     

Microwave-assisted synthesis of 5-aryl-3-hydroxy-2-oxindole derivatives and evaluation of their antiglaucomic activity

A set of new 5-aryl-3-hydroxy-2-oxindoles was synthesized by decarboxylative condensation of the corresponding 5-aryl-substituted isatins with malonic or cyanoacetic acids under microwave irradiation. The antiglaucomic activity of the obtained compounds was evaluated. The most water soluble compounds can reduce the intraocular pressure (IOP) up to 2 Torr.     

Synthesis of bicyclic pyrimido[2,1-<Emphasis Type="Italic">b</Emphasis>][1, 3]thiazines based on 3,4-dihydropyrimidine-(1H)-2-thiones

Bicyclic pyrimido[2,1-b][1, 3]thiazines were produced by the acylation of 4-aryl-substituted 3,4-di-hydropyrimidine(1H)-2-thiones with 3-bromopropionyl chloride, and their structures were proved by the data from X-ray crystallographic analysis.     

A New Route to 6-Aryl-substituted 3,4-Dihydronaphthalene Derivatives via Pd (O)-Catalyzed Cross-Coupling Reaction of Aryl Zinc Chlorides with an Aryl Triflate

A procedure for the Pd (O)-catalyzed cross coupling of the triflate of 6-hydroxy-3,4-dihydronaphthalene-2-methylcarboxylate with various aryl zinc chlorides was developed, which represents an efficient approach to 6-aryl-substituted naphthalene derivatives.     

Synthesis of 3-Substituted Arylpyrazole-4-carboxylic Acids

A method was suggested for preparing previously unknown 3-aryl-substituted pyrazole-4-carboxylic acids, involving Vilsmeier formylation of semicarbazones of 26 available mono- and disubstituted acetophenones and 2-acetylthiophene followed by oxidation of the resulting 3-aryl-substituted pyrazole-4-carboxaldehydes under the action of potassium permanganate. The mechanism of the formylation reaction is discussed. The method successfully works even with acetophenones containing alkyl substituents. In the latter case, an additional stage that involves isolation of pyrazole-4-carboxylic acids as their silyl esters is used.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 829–835.Original Russian Text Copyright © 2005 by Lebedev, Lebedeva, Sheludyakov, Kovaleva, Ustinova, Kozhevnikov.     

Regiospecific synthesis of 1-arylpyrazoles

A new regiospecific synthesis of 1-aryl-substituted pyrazoles by reaction of aryl-hydrazines with β-aminoenones is reported.     

Gas-Phase ring-chain tautomerism in 1,3-oxazines. Does it exist?

Gas-phase ring-chain tautomeric equilibria with eight 2-phenyl-substituted perhydro-1,3-oxazines and six 2-aryl-substituted l,2-dihydro-4H-3,1-benzoxazines were studied by recording their mass spectra Finder different conditions. Their fragmentation behaviour was also studied using metastable ion analysis and exact mass measurement. For the monocyclic compounds the existence of tautomerism was apparent and it resembled that found in non-polar solvents. In contrast, benzoxazines gave little evidence for the presence of the open-chain forms.     

Catalytic enantioselective synthesis of chiral γ-butyrolactones

A tandem catalytic asymmetric aldol reaction/cyclization of β,γ-didehydro-γ-lactones with aldehydes was achieved using chiral tin dibromide as a chiral precatalyst and sodium alkoxide as a base precatalyst. Optically active trans-β,γ-disubstituted γ-butyrolactones were selectively obtained in moderate to high yields with up to 99% ee from γ-aryl-substituted β,γ-didehydro-γ-butyrolactones and bulky aliphatic aldehydes.     

Liquid crystalline N-aryl-β-aminovinyl ketones and their complexes with lanthanides

Liquid crystalline lanthanide complexes with N-aryl-substituted β-aminovinyl ketones were synthesized for the first time. The complexes give rise to smectic A mesophase and are stable only in the solid state; in going to solution, they dissociate with formation of the initial ligand.     

Chiral sulfinamide/achiral sulfonic acid cocatalyzed enantioselective protonation of enol silanes

The application of chiral sulfinamides and achiral sulfonic acids as a cocatalyst system for enantioselective protonation reactions is described. Structurally simple, easily accessible sulfinamides were found to induce moderate-to-high ee's in the formation of 2-aryl-substituted cycloalkanones from the corresponding trimethylsilyl enol ethers.     

Synthesis of symmetrical α-alkyl- and α-arylalkylbenzyl and diarylmethyl ethers by HCl-catalyzed intermolecular dehydration

α-Alkyl-, α-arylalkyl-, and α-aryl-substituted benzyl alcohols were converted into the corresponding symmetrical dibenzyl ethers in the presence of a catalytic amount of 10% aqueous HCl both in methylene chloride and under solvent-free conditions. Analogous reactions in dioxane and on heating afforded mainly the corresponding arylalkenes, whereas symmetrical dibenzyl ethers were formed as minor products.     

Cycloaddition d'azides aux sels de nitrilium; obtention de sels de tetrazolium et de tetrazolines

The reaction of nitrilium salts with azides allows the synthesis with good yields of 1,4,5-alkyl or -aryl-substituted tetrazolium salts. The mechanism of this reaction is discussed. Reduction or alkylation of these tetrazolium salts leads to the corresponding tri- or tetra-substituted tetrazolines.     

Expanded dipyrrins with electron-withdrawing substituents: broad range of absorption in the visible region

Reaction of meso-aryl-substituted dipyrromethanes with tetracyanoethylene led to generation of a mono-tricyanovinyl-substituted species as well as an expanded dipyrrin analogue bearing both a dicyanomethylene and a tricyanovinyl substituent at the α-positions. These novel compounds exhibit absorption spectral features perturbed by the electron-withdrawing substituents. Unique protonation-induced spectral changes were also disclosed.     

Pd-Catalyzed Heterocyclization During Sonogashira Coupling: Synthesis of 3-Aryl-substituted Imidazo[2,1-b]thiazoles

Abstract

The reaction of 4,5-diphenyl-2-propargylmercaptoimidazole with various aryl iodides catalyzed by Pd-Cu in the presence of triethylamine as base in dimethyl formamide (DMF) leads to the formation of 3-aryl-substituted imidazo[2,1-b]thiazoles.     

Selective introducing of aryl and amino groups: reaction of benzanthrone and organometallic reagents

The reaction of benzanthrone and aryl magnesium bromides produced 6-aryl-substituted benzanthrones in moderate to good yields. Similarly, 6-alkylaminobenzanthrones were selectively prepared by the reaction of benzanthrone and lithium alkylamides. In contrast, for the lithium arylamides, the arylamino groups were selectively introduced at the 4-position of the benzanthrone.     

Double reduction of cyclic aromatic sulfonamides: a novel method for the synthesis of 2- and 3-aryl-substituted cyclic amines

The facile double reduction of bicyclic aromatic sulfonamides was used to synthesize a variety of 2- and 3-aryl-substituted pyrrolidines and 2-phenylpiperidine. The method features a combined nitrogen protection and a traceless tether for the transposition of the aromatic moiety from nitrogen to carbon.