Homotransmetallation des halogeno-3 pyridines bromees en -2 ou -4 par le n-butyllithium. proposition d'un nouveau mecanisme de telesubstitution du brome

These are new examples of the homotransmetalation reaction. Instead of the ordinary bromo-metal exchange it is possible to obtain selectively from the 2-bromo 3-fluoro or 2-bromo 3-chloro pyridines the 2-bromo 3-halogeno 4-lithio pyridines, which is very interesting for synthetic utility. From the 4-bromo 3-halogeno pyridines, we can see an isomerization with an halogen dance mechanism and we obtain the 5-bromo 3-halogeno 4-lithio pyridines. In the case of the 2-bromo 3-fluoro pyridine we explain a telesubstitution of bromine from 2 to 4 by a transistory homotransmetalation reaction during the Li-Br exchange.     

Variation in the regioselectivity of levulinic acid bromination in ionic liquids

The reaction of levulinic acid and its esters with bromine in ionic liquids results in the formation of 3-bromo derivatives as the major products and not the 5-bromo substituted isomers, which are typically formed in organic solvents. The bromination of levulinic acid in ionic liquids in the presence of urea leads to the formation of 5-bromolevulinic acid.     

Nitrone—XI Isoxazolidin-verbindungen—VIII : N-substituierte 5-isoxazolidinone durch reformatzky-reaktion mit nitronen

The two step procedure of the Reformatzky reaction with nitrones enables the synthesis of 2-alkyl 3-aryl 5-isoxazolidinones from α-bromo esters and such nitrones, which are too basic for the one step procedure, Diethyl α-bromo methylmalonate is especially suited for the Reformatzky reaction with nitrones, yielding the E-isomer of the corresponding isoxazolidinone. Reaction of ethyl α-bromo butyrate yields chiefly the Z-isomer, from which result conclusions are drawn concerning the transition state of the primary addition step.     

Structure and tautomerism of 4-bromo substituted 1H-pyrazoles

The tautomerism in the solid state and in solution of five 4-bromo-1H-pyrazoles has been studied by multinuclear magnetic resonance spectroscopy and, for one of them, by X-ray crystallography (3,4-dibromo-5-phenyl-1H-pyrazole). When there is a bromine atom at position 3(5), in all cases, the tautomer present in the solid state is the 3-bromo one. In solution, the same tautomer is the major one. DFT calculations justify the predominance of 3-bromo tautomers over 5-bromo ones and provide some useful chemical shifts obtained through GIAO calculations.     

FT-IR, Raman and DFT study of 2-amino-5-fluorobenzoic acid and its biological activity with other halogen (Cl, Br) substitution

The Fourier-transform Raman and infrared spectra of 2-amino-5-fluoro benzoic acid has been recorded and analyzed. The optimized geometry of the other halogen substitution (Cl, Br) have been computed with the help of density functional theory. The detailed interpretation of vibrational spectra of 2-amino-5-fluoro benzoic acid have performed in terms of potential energy distribution analysis. Natural bond orbital analysis on 2-amino-5-fluoro benzoic acid, 2-amino-5-chloro benzoic acid and 2-amino-5-bromo benzoic acid has been carried out for various intramolecular interactions that are responsible for the stabilization of the molecule. The pKa values of 2-amino-5-fluoro benzoic acid, 2-amino-5-chloro benzoic acid and 2-amino-5-bromo benzoic acid are computed using MOPAC and it is related with HOMO-LUMO energy difference obtained from Gaussian 03 software. The biological activity of 2-amino-5-fluoro benzoic acid has been predicted based on these values. The inhibition activity of 2-amino-5-bromo benzoic acid with the protein tyrosine kinase 3LQ8 is simulated by using Autodock software.     

Synthesis of 7-Bromo/5,6-Dimethyl-4 H -1,4-Benzothiazines and Their Conversion into Sulfones

The synthesis of 7-bromo/5,6-dimethyl-4 H -1,4-benzothiazines and their conversion into sulfones is reported. The 7-bromo/5,6-dimethyl-4 H -1,4-benzothiazines were synthesized by the condensation and oxidative cyclization of 2-amino-5-bromo/3,4-dimethylbenzenethiol with g -diketones in dimethyl sulfoxide. The reaction is believed to proceed via an enaminoketone system. 4 H -1,4-Benzothiazine sulfones have been synthesized by the oxidation of 4 H -1,4-benzothiazines using 30% H 2 O 2 in glacial acetic acid. The structures of all newly synthesized compounds have been confirmed by elemental analysis and spectral studies.     

2-(3-Acetylamino-2,2-dimethylcyclobutyl)-methyl-4(3H)-quinazolinones

Beckmann rearrangement of N-[3-(1-hydroxyimino)ethyl-2,2-dimethylcyclobutyl]acetylanthranilic acid, and its 5-bromo and 4-chloro derivatives gives the corresponding N-(3-acetylamino-2,2-dimethylcyclobutyl)acetylanthranilic acids. Treatment of these acylanthranilic acids with formamide gives 2-(3-acetylamino-2,2-dimethylcyclobutyl)methyl-4(3H)-quinazoline and its 6-bromo and 7-chloro derivatives.     

On the synthesis and animation of 5-chloro-and 5-bromo-1,7-naphthyridine

A new synthesis of 5-chloro- and 5-bromo-1,7-naphthyridine, using 8-amino-1,7-naphthyridine as starting material is described. On amination with potassium amide in liquid ammonia, the 5-bromo compound undergoes a tele-amination into 8-amino- and 2-amino-1,7-naphthyridine and a Chichibabin reaction yielding 8-amino-5-bromo-1,7-naphthyridine. The reaction with the 5-chloro compound occurs at a much lower rate than the 5-bromo compound and only gives 8-amino-5-chloro-1,7-naphthyridine in a small yield. Convincing ¹H-nmr evidence is presented, showing that the 5-bromo- and 5-chloro-1,7-naphthyridine give addition of the amide ion at position 8 and that the 5-chloro compound also gives addition at position 2.     

A facile two-step synthesis of 8-arylated guanosine mono- and triphosphates (8-aryl GXPs)

We report a simple and high-yielding two-step procedure for the preparation of 8-arylated guanosine mono- and triphosphates (8-aryl GXPs). The key step of our synthesis is the Suzuki-Miyaura coupling of unprotected 8-bromo GMP and 8-bromo GTP with various arylboronic acids in aqueous solution. The 8-bromoguanosine 5'-phosphates required as cross-coupling substrates were prepared from 8-bromoguanosine via an optimised Yoshikawa procedure.     

New approach to the synthesis of 2,2':5',2'-terthiophene-5,5'-and 2,2':5',2':5',2''-quaterthiophene-5,5''-dicarboxylic acids

Chemistry of Heterocyclic Compounds - The reaction of bromosuccinimide with esters of 3-substituted 2,2'-bithiophene-5-carboxylic acids was used to obtain their 5'-bromo derivatives, which...     

Synthesis of 1,3-dioxanes from furan aldehydes

Six new cyclic acetals have been synthesized by the reaction of furfural and its 5-methyl, 5-bromo, 5-chloro, and 5-nitro derivatives and furyl-acrolein with 1,1,1-tris(hydroxymethyl)propane. Their UV and IR spectra are given.     

Zirconium(IV) Thorium(IV) and Dioxouranium(VI) Complexes of Salicylidene o-Aminobenzothiol

Salicylidene-o-aminobenzothiol and its 5-chloro and 5-bromo derivatives, dibasic tridentate Schiff bases, dervied from the condensation of o-aminothiol and Salicylaldehyde, 5-chloro salicylaldehyde and 5-bromo salicylaldehyde, were used for coordination with Zr(IV), Th(IV) and UO₂(VI) metal inos. The I:I (metal-ligand) stoichiometry of these complexes is shown by elemental analysis and conductometric titrations. Molecular structure of these complexes are proved by Infra-red spectroscopy and thermogravimetric analysis. Magnetic susceptibility measurements of Zr(IV), Th(IV) and UO₂(VI) complexes show their diamagnetic and octahedral geometry. Results show that all the complexes have solvent molecules in coordination with metal ion.     

Derivatives of 1-(2-pyridyl)-4,5,6,7-tetrahydroindazole

In reaction of oxidation of 1-(2-pyridyl)3,6,6-trimethyl-4-oxo-4,5,6,7-tetrahydroindazole, the corresponding 4,5-dioxoindazole is obtained, and then 1-(2-pyridyl)-3-methyl-4-carboxy-5-(2-methyl-2-carboxypropyl)pyrazole; in bromination reaction, a series of 5-bromo and 7-bromo derivatives is obtained. From 4,5-dioxoindazole with hydrazides of acids, a series of 4-oxo-5-acylhydrazono derivatives is obtained, and also 1-(2-pyridyl)-3,6,6-trimethyl-4-oxo-5-tosylhydroindazole, which, under the action of caustic, gives the 4-oxo-5-diazo derivative.Riga Technical University, Riga LV-1658. Translated from Khimiya Geterotsiklicheskikh Soerdinenii, No. 3, pp. 351–354, March, 1995. Original article submitted December 29, 1994.     

Mechanism of the Debromination in Heterocyclization Using α,α-Dibromocarbonyl Compounds as Synthons

α,α-dibromocarbonyl compounds on condensation with phenylacetic acid or thioamide give the furanone or thiazole instead of the expected corresponding 5-bromo products. The mechanistic study have been made to find the reaction path way.     

Synthesis,methylation, and acylation of 1,2-dihydrodeoxyvasicinones and their homologs

2,3-Trimethylene- and 2,3-pentamethylene-1,2,3,4-tetrahydro-4-quinazolones and their 6-methyl and 6-bromo derivatives have been obtained by the reduction of deoxyvasicinone and its 6-methyl and 6-bromo derivatives and also their seven-membered homologs at the cycloalkane ring with sodium tetrahydroborate in ethanol. The alkylation and acylation reactions of the above-mentioned reducing compounds have been studied. Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 659–663, September–October, 1990.     

Synthesis, methylation, and acylation of 1,2-dihydrodeoxyvasicinones and their homologs

2,3-Trimethylene- and 2,3-pentamethylene-1,2,3,4-tetrahydro-4-quinazolones and their 6-methyl and 6-bromo derivatives have been obtained by the reduction of deoxyvasicinone and its 6-methyl and 6-bromo derivatives and also their seven-membered homologs at the cycloalkane ring with sodium tetrahydroborate in ethanol. The alkylation and acylation reactions of the above-mentioned reducing compounds have been studied.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 659–663, September–October, 1990.     

Cobalt-Catalyzed α-Arylation of Substituted α-Bromo α-Fluoro β-Lactams with Diaryl Zinc Reagents: Generalization to Functionalized Bromo Derivatives

A cobalt-catalyzed cross-coupling of α-bromo α-fluoro β-lactams with diarylzinc or diallylzinc reagents is herein disclosed. The protocol proved to be general, chemoselective and operationally simple allowing the C4 functionalization of β-lactams. The substrate scope was expanded to α-bromo lactams and amides, α-bromo lactones and esters as well as N - and O-containing heterocycles.     

Isothiazoles IX. Halogenation of 2-substituted-4-isothiazolin-3-ones

Bromination of 4-isothiazolin-3-ones, I, gave the 4-bromo derivatives, III, in good yields, while formation of 4,5-dibromo derivatives, IV, was much more difficult. In contrast, chlorination of I, even under mild conditions, gave primarily 4,5-dichloro derivatives, VI, and lesser amounts of the 4-chloro derivatives, V. Vigorous bromination of the 4-methyl analog of I gave the 5-bromo derivatives, VIII, whereas mild chlorination gave predominantly the 4,5,5-trichloro derivatives, X.     

5-vinyl pyrimidines. I. Synthesis

A total synthesis of 5-vinyl pyrimidine and some of its substituted derivatives is described. The following vinyl pyrimidines have been prepared: 5-vinyl pyrimidine, 5-vinyl-4,6-dimethoxy pyrimidine, 5-(α-bromo) vinyl-4,6-dimethoxy pyrimidine.     

New Re(I) tricarbonyl-diimine complexes with N,N′-bis(substituted benzaldehyde)-1,2-diiminoethane Schiff base ligands: Synthesis,spectroscopic and electrochemical studies and crystal structures

The syntheses, structures and spectroscopic properties of tricarbonylrhenium(I) complexes with N,N′-bis(2-bromo, 4-bromo, 4-chloro and 3-methoxybenzaldehyde)-1,2-diiminoethane Schiff base ligands have been investigated in this paper. Characterization of these complexes was carried out with FTIR, NMR, UV–Vis spectroscopy, elemental analysis and X-ray crystallography. The electrochemical behavior of the investigated complexes has been studied by cyclic voltammetry. The crystal structures of the 4-chloro, 4-bromo and 4-methoxy substituted complexes are stabilized by intermolecular C–H?Cl and C–H?O hydrogen bonds. The remarkable features of the 2-bromo, 4-bromo and 4-chloro substituted complexes are short intermolecular halogen–oxygen contacts. In the 4-bromo complex, short intermolecular Br?O and O?O contacts link neighboring molecules along the [1 0 0] direction, which are further stabilized by short intermolecular π?π interactions. In 2-bromo complex, intermolecular Br?O interactions link neighboring molecules into 1D extended chains along the [0 1 0] and [0 0 1] directions, forming a 2D network which is parallel to the bc-plane.