Bromination of 2-thiazolylhydrazones

Bromination of the 4-carbethoxy- and 4-carboxy-2-thiazolylhydrazones of aldehydes and ketones occurs principally at the 5 position of the thiazole ring. In the case of aldehyde hydrazones an excess of bromine leads to substitution of the methine hydrogen atom and to intramolecular cyclization of the intermediate halohydrazone to 1,2,4-triazolo[3,4-b]thiazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 257–262, February, 1993.     

Bromination of 2-acetyl-5-methylfuran

The bromination of 2-acetyl-5-methylfuran by bromine and N-bromosuccinimide was studied. The action of N-bromosuccinimide on 5-methyl-2-acetylfuran in various solvents leads to mixtures of an -bromo ketone, a 5-bromomethyl derivative, and 5-bromomethyl--bromo ketone. The use of 2,2-azobisisobutyronitrile as activator of the radical process does not make the reaction selective but promotes bromination at the methyl group of the ring. A selective method for the synthesis of 2-(bromoacetyl)-5-methylfuran by the bromination of 2-acetyl-5-methylfuran with bromine was developed.Latvian Institute of Organic Synthesis, Riga. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 184–186, February, 1999.     

Bromination of 1-alkyl-2-pyridones

The corresponding monobromides were obtained in the bromination of 1-alkyl-2-pyridones with bonded bromine (with N-bromosuccinimide and dioxane dibromide). The conditions under which the yields of the mixtures of isomers were 60–80%, and almost no dibromides were obtained, were found. It was established that the ratios of the 3- and 5-bromo isomers depend on the character of the brominating agent.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1662–1664, December, 1982.     

Bromination of 2, 3-dimethylindole

In bromination of indoles, the bromine atom will most probably enter at position 2 or 3. For example, indole and 2-methylindole [1] brominate at position 3, while some 3-substituted indoles [2] brominate at position 2. In the case of 2, 3-dimethylindole it was shown [3], that bromine does not enter the benzene ring, as would have been expected, but adds to the active 2, 3 (double) bond of the indole.     

Bromination and oxidation of 2-oxaadamantane

A marked decrease in reactivity has been shown for oxaadamantane towards bromination and oxidation when compared with adamantane. The mono- and dihydroxy and acetoxy substituents in the products occupied positions in the molecule remote from the oxa bridge.M. V. Lomonosov State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedineii, No, 5, pp. 608–612, May, 1994. Original article submitted April 26, 1994.     

Bromination of 3-acyl-2-aminoindoles

Unlike 3-acylindoles, 3-acyl-2-aminoindoles display high selectivity on being electrophilically attacked in the benzene ring, and are substituted at the 6-position. At the same time, an unco-subsitution of the acyl group takes place (to the greatest extent — the formyl group). Direct bromination of 3-acyl- and 3-cyano-2-aminoindoles provides the 6-bromo- and 6,4-dibromo-2-aminoindoles and their derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 486–490, April, 1990.     

Selective Benzylic Bromination of 2-Methylnaphthalene

A practical synthesis of 2-(bromomethyl)naphthalene (1), by selective benzylic bromination of 2-methylnaphthalene (2), with bromine in heptane in the presence of lanthanum acetate hydrate is described.     

Bromination of 2-acetylthiophene and its derivatives

A new method has been developed for the bromination of thiophene and its derivatives. The method consists in the action of N-bromosuccinimide in acetic anhydride and glacial acetic acid on the thiophene derivatives. In the bromination of 2-acetylthiophene and its derivatives, the bromine replaces the hydrogen atom in the 5 position of the thiophene ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 185–187, February, 1973.     

Bromination of vinyl derivatives of benzimidazole-2-thione

The reaction of vinyl derivatives of benzimidazole-2-thione with bromine was investigated. It is shown that the principal reaction is the addition of the halogen to the double bond of the vinyl group. Depending on the structure of the starting vinyl derivative, elimination of hydrogen bromide or halogenation at the heteroring nitrogen atom, which leads to the formation of hydrohalides, is subsequently possible.Translated, from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1092–1094, August, 1982.     

Stereoselective Bromination of 2-Vinyl Chromones Using NBS

A simple one-step synthetic methodology for stereoselective synthesis of E- and Z-3-bromo-2-vinyl chromones in quantitative yield in polar solvents under ambient conditions without the use of catalysts is reported.     

Bromination of sydnones. II Bromination of 3-(2-aminophenyl)sydnone and related compounds

Bromination of 3-(2-aminophenyl)sydnone 2 under a variety of conditions is reported. The products obtained are interrelated by a series of subsequent reactions. One major product is the bromoaryl compound 8, the first example of bromination on the aryl rather than sydnone ring when the two are in competition. Surprisingly, bromoaminosydnone 9, prepared from its nitro analogue, was not among the products obtained by direct bromination of 2.     

Bromination of arylfurans

The bromination of 2-arylfurans has been studied. The structures of the compounds obtained have been determined with the aid of NMR spectra.Translated from Khimiya Geterotisiklicheskikh Soedinenii, No. 4, pp. 450–454, April, 1980.     

Bromination of terephthalaldehyde

Conclusions The direct bromination of terephthalaldehyde in the presence of excess anhydrous AlCl₃ leads to the formation of terephthaloyl bromide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 480–481, February, 1977.     

Organoboron compounds: CDV. Bromination of 2-isopropyl-2-boraadamantane

Bromination of 2-isopropyl-2-boraadamantane in CH₂Cl₂ proceeds simultaneously by both radical and electrophilic mechanisms. The first involves elimination of HBr and formation of 2-(2-bromo-2-propyl)-2-boraadamantane; this rearranges, under the action of nucleophilic reagents, to a derivative of 4-borahomoadamantane, which converts, on oxidation, to 3α-hydroxy-7α-(2-hydroxy-2-propyl)bicyclo[3.3.1]-nonane. The second direction includes cleavage of a BC(isopropyl) bond with formation of i-PrBr and 2-bromo-2-boraadamantane, oxidation of which leads to 3α, 7α-dihydroxybicyclo[3.3.1]nonane. In the presence of H₂O, a solvated Br⁺ also takes part in the bromination, which results in formation of hydroxy (3-noradamantyl)isopropylborane, which is oxidized to 3-noradamantanol. Depending on the reaction conditions one of the three possible directions may predominate.     

Magnesium Chloride Directed Aldol and Bromination of 2-Acetylfuran

Reaction of 2-acetylfuran with diisopropylethylamine and magnesium chloride followed by bromination gave 1,3-difuryl-3-hydroxy-1-butanone and 1,3-difuryl-4-bromo-3-hydroxy-1-butanone. Under similiar conditions 2-acetythiophene failed to react.     

Bromination of Binor-S

Bromination of binor-S resulted in a mixture of products containing several pairs of isomers. Three major processes were found to be involved in the reaction mechanism, i.e., bromination, hydrobromination, and dehydrobromination. The structures of nine compounds derived from dibromide 6 were identified by spectroscopic methods. Yields between isomers were rationalized by comparison of their relative strain energies calculated by force field model (MM2). The crystal structures of a tribromide (9) and a pentabromide (15) were solved by X-ray diffraction analyses. Their crystal packing patterns indicated the existence of attractive interactions among the bromine atoms.     

Bromination of emodin

Using emodin as an example, it has been shown that in the bromination of hydroxyanthraquinones the qualitative composition and quantitative ratio of the reaction products depend on the nature of the brominating agent and the solvent, the ratio of the rea Lants, and the temperature regime. In order to obtain bromo-3-methyl-1,6,8-trihydroxyanthraquinone it is recommended to use dioxane dibromide in acid solution as the brominating agent, and to obtain 5-bromo-3-methyl-1,6,8-trihydroxyanthraquinone the same reagent in dioxane solution. The optimum conditions for obtaining 3-bromomethyl-1,6,8-trihydroxyanthraquinone by the methods of initiated bromination and photobromination have been selected.S. M. Kirov Kazakh State University, Alma-Ata. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 618–621, September–October, 1990.