Amidines as potent nucleophilic organocatalysts for the transfer of electrophilic bromine from N-bromosuccinimide to alkenes

(±)-iso-Amarine is a potent organocatalyst at 1 mol % loading for both the bromoacetoxylation of alkenes with added acetic acid and bromolactonisation of unsaturated carboxylic acids with stoichiometric NBS as the electrophilic bromine source. A simple bromoamidine with an N-Br bond has been characterised crystallographically for the first time. Asymmetric induction in the bromination reactions with enantiopure amidines was zero.     

Transformations of sclareol oxide by bromination. Synthesis of driman-8α, l l-diol from sclareol oxide

Depending on reaction conditions, the reaction of sclareol oxide with N-bromosuccinimide affords either 12-bromo- or 12,16-dibromosclareol oxide, whereas the reaction of sclareol oxide with bromine in methanol gives l2-monobromide or (13S)-1 1,12-dibromo-8,13-epoxy-13-methoxy-14,15-bisnorlabdane. Dehydrobromination of the latter with potassium hydroxide in toluene in the presence of polyethylene glycol gives (13S)-12-bromo-8, 13-epoxy-l3-methoxy-14,15-bisnorlabd-11-ene, ozonolysis of which followed by reduction of the ozonide with LiAlH₄ affords drimane-8, 11 I-diol.Translated fromIzvestiya Akademi Nauk. Seriya Khimicheskaya, No. 11, pp.2780–2784, November,1996     

A reaction of 6-bromo-1,2-naphthoquinone with tri(<Emphasis Type="Italic">n</Emphasis>-butyl)phosphine: A convenient route to phosphorus-containing 1,2-naphthoquinones and 1,2-dihydroxynaphthalenes

A reaction of 6-bromo-1,2-naphthoquinone with tri(n-butyl)phosphine gave 2-hydroxy-4-tri(n-butyl)phosphonionaphth-1-olate (betaine with the P—C bond). When treated with bromine, this betaine changed into (6-bromo-1,2-dihydroxy-4-naphthyl)tri(n-butyl)phosphonium bromide and (6-bromo-1,2-dioxo-1,2-dihydro-4-naphthyl)tri(n-butyl)phosphonium bromide in the ratio ∼1: 1. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 534–536, March, 2007.     

An efficient vanadium-catalyzed bromination reaction

An efficient catalytic oxidative bromination of arenes, alkenes, and alkynes in aqueous media was achieved under relatively mild conditions by using NH₄VO₃ catalyst combined with H₂O₂, HBr, and KBr. Dodecyltrimethylammonium bromide was found to serve as an efficient surfactant to facilitate the NH₄VO₃-catalyzed bromination in aqueous media.     

Boron（Ⅲ） Tribromide or Tianium （Ⅳ） Bromide and Lewis Base Promoted Baylis—Hillman Reaction

It was found that,when the Baylis-Hillman reaction of arylaldehydes with methyl vinyl ketone was carried out at below -20℃ in the presence of boron (Ⅲ） tribromide or titanium (Ⅳ） bromide using a catalytic amount of Lewis base such as amine,the brominated compounds and the Baylis-Hillman adducts could be obtained as the major products in good yields for various aryl aldehydes.But at room temperature,the elimination products were the major products.In addition,the palladium catalyzed allylic substitution reactions of the elimination products were also examined.     

Bromination of <Emphasis Type="Italic">tert</Emphasis>-Butyl Esters of 7α-Chloro and 7-Alkylidenedeacetoxycephalosporanic Acid Sulfones

The action of N-bromosuccinimide on tert-butyl esters of 7α-chloro- and 7-alkylidenedeacetoxycephalosporanic acid sulfones upon irradiation with visible light leads to the formation of a mixture of the product of allylic bromination of the 3-methyl group, namely, 3-bromomethyldeacetoxycephalosporanate, and the product of replacement of a proton at C₍₂₎ in the latter, namely, 2-bromo-3-bromomethyldeacetoxycephalosporanate. Small amounts of E-isomers were also obtained in the case of the Z-isomer of the 7-(4-nitrobenzylidene) derivative. In the case of the 7α-chloro derivative only substitution of one or two protons at C₍₂₎ occurs during bromination without irradiation, the same as the isomerization of the double bond in the cepheme system.Dedicated to Academician N. K. Kochetkov on the occasion of this ninetieth birthday.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 767–774, May, 2005.     

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.     

制备2,4,6-三甲基苯甲醛的新方法

1,3,5-三甲苯与溴素在水溶液中反应生成2,4,6-三甲基溴苯(1,收率90%);1制备成格氏试剂再与甲醛反应得到2,4,6-三甲基苄醇(2,收率79%)。2经铬酸氧化得2,4,6-三甲基苯甲醛(3,收率90.3%)。3的总收率达64.2%,纯度97%。2和3的结构经1H NMR和MS确证。     

Functionalization of one or two methyl groups in the [Cp*<Subscript>2</Subscript>RuBr]<Superscript>+</Superscript>Br<Superscript>−</Superscript> complex in the reaction with bromine

The reaction of [Cp*₂RuBr]⁺Br⁻ with bromine in CH₂Cl₂ (CD₂Cl₂) in an inert atmosphere at room temperature produces the complexes [Cp*Ru(Br)C₅Me₄CH₂Br]⁺Br₃ ⁻ (syn conformer), [Cp*Ru(Br)C₅Me₃(CH₂Br)₂]⁺ (syn and anti conformers), and [Ru(Br)(C₅Me₄CH₂Br)₂]⁺ (syn conformer). All complexes were characterized by ¹H and ¹³C NMR spectroscopy; the former complex, by elemental analysis. These complexes were also prepared by the reaction of [Cp*RuC₅Me₄CH₂]⁺BF₄ ⁻ with bromine in CH₂Cl₂. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2712–2718, December, 2005.     

Synthesis and crystal structure of 29,30-dibromoallobetulin

The bromination of betulin with bromine was descibed. The reaction in chloroform proceeded smoothly to form 29,30-dibromoallobetulin in 80% yield. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 153–155, March–April, 2006.