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Bromination with bromine

This ionic mechanism is supported by kinetic data. A free radical mechanism has been proposed for the unique bromination (with bromine) of 3a, 12a-diacetoxypregnan-20-one ethylene ketal, which gives the 21-bromo derivative in excellent yield. ... [Pg.206]

Bromination of di-2-thienylmethane is best achieved with a bro-mide-bromate mixture in a heterogenous system. Conventional bromination with bromine in CCU was accompanied by marked tar formation. Bromination occurs in the 5- and 5 -positions of the rings as proved by the preparation of di-(5-bromo-2-thienyl) methane... [Pg.56]

Treatment of 2,7-di-/ert-butylthiepin (1) either directly with bromine at — 78 °C, or with pyridinium bromide perbromide at room temperature, gives the thiophene compound 2. In contrast, bromination with bromine-1,4-dioxane complex or pyridinium bromide perbromide in the presence of acetic acid leads to the thiopyran derivative 3.87 To account for these results a homothiopyrylium ion has been proposed as a common intermediate, formed by electrophilic bromination at C4 in the first step. [Pg.102]

The results were compared with the bromination with bromine. It was apparent that bromine gave /jora-bromides exclusively except 2-allylphenol. As the reaction of 2-allylphenol with bromine gave the mixture of many products (bromine adduct as main product, some ring bromides as by-products, etc.), 2-allylphenol was treated with benzyltrimethylammonium tribromide (BTMA Br3) which was already developed as mild and easy bromine (ref. 10). [Pg.11]

The difference in stability between the two is not very marked, however, reflecting the highly activated state of the nucleus, and ready substitution will take place at the 3-position if the 2- is blocked. It is, indeed, not uncommon to get substitution on all four carbon atoms, e.g. on bromination with bromine in ethanoic acid. [Pg.167]

Thienylaminomethylenemalonates (1536) were brominated with bromine in a mixture of pyridine and chloroform to yield the 5-bromo deriva-... [Pg.315]

Nitration with concentrated nitric acid in acetic anhydride and glacial acetic acid affords a mixture of 2- and 3-nitrothiophenes (in the ratio 6 1) (Scheme 6.33). However, bromination with bromine in diethyl ether and 48% hydrobromic acid, starting at -25 °C and allowing the reaction temperature to rise to -5 °C, gives 2-bromothiophene. If the experiment is initiated at -10 °C and the temperature is then allowed to rise to + 10 °C, 2,5-dibromothiophene is formed. 2,3,5-Tribromination occurs in 48% hydrobromic acid, starting the experiment at room temperature and allowing the temperature to rise to 75 °C. Acetylation with acetyl chloride in the presence of the Lewis acid tin(IV) chloride gives 2-acetylthiophene, and efficient 2-formylation takes place under Vilsmeier conditions (see Section 6.1.2). [Pg.91]

In delineating the scope of the bromination-nucleophilic sulfur reaction, two difficulties have been encountered. Bromination with bromine is not successful with tertiary hydrogens such as those present in prolyl derivatives (72CB625). Bromination can be accomplished by means of N-bromosuccinimide in presence of 2,2 -azobisisobutyronitrile however, in this case, 3,6-dialkylpiperazine-2,5-diones yield tetrabromo derivatives. These could be successfully utilized for the required purpose, as shown in Scheme 37. The trick consisted of displacing the bromine atoms attached to the ring by methoxy groups, followed by debromination and thiolation (75BCJ605). [Pg.233]

In the original patent published by Merck in 1995, rofecoxib (2) was synthesized in three steps from the known 4-(methylthio)acetophenone (10), prepared from the Friedel-Crafts acylation of thioanisole. As depicted in Scheme 2, oxidation of sulfide 10 using an excess of magnesium monoperoxyphthalate hexahydrate (MMPP, an inexpensive, safe and commercially available surrogate for w-CPBA) gave rise to sulfone 11, which was subsequently brominated with bromine and AICI3 to afford 2-bromo-l-(4-(methylsulfonyl)phenyl)ethanone (12). After recrystallization from 1 1 EtOAc/hexane, the pure phenylacyl bromide 12 was then cyclo-condensed with phenylacetic acid under the influence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to deliver rofecoxib (2) in... [Pg.14]

When the same reaction is performed with adamantanone dinitrophenylhydrazone (DNP) or adamantanone O-mcthyloxime (OMO), the yields of 2,2-difluoroadamantanc are 65 and 50%, respectively. 4-tert-Butylcyclohexanone is converted via its azine, DNP or OMO into 4-tert-butyl-l.l-difluorocyclohexanc in 65, 75 or 50% yield, respectively. Similar results are obtained with aliphatic straight-chain ketones. Decan-2-one azine and decan-2-one DNP can be transformed into 2,2-difluorodecane in 60 and 80% yield. Deactivated aromatic rings, e.g. in 3-nitroacetophenone, do not undergo bromination with bromine trifluoride and the action of 2 equivalents of bromine trifluoride on 3-nitroacetophenone O-methyloxime results in 90% yield of 1-(1. l-difluorocthylj-S-nitrobenzene.122... [Pg.256]

Bromo derivatives of 2-amino-3-chloro- and 2-amino-3-bromo-pyrazines are obtained by bromination with bromine in 20% hydrobromic acid at 5°. Similar treatment of 2-amino-5-bromopyra-zine-3-carboxylic acid gives 2-amino-3,5-dibromopyrazine.291 292... [Pg.157]

This oxidation is used in situ for aromatic and side-chain brominations with bromine or hydrogen bromide302,303. Typical industrial examples are brominations of bisphenol A (equation 43)304 305, diphenyl ether306 and nitrotoluene (equation 44)307,308. [Pg.555]

Bromination with bromine in thionyl chloride or sulfur monochloride and pyridine also gave 3-bromoquinoline (65%) and 4-bromoisoquinoline from the parent heterocycles (60JA4430). [Pg.383]

Bromination with bromine/sulfuric acid/silver sulfate of benzo[c]cinno-line gives the 1- and 4-monobromo derivatives in a ratio of 2.3 1 [79JCS(P1)1503], contradicting an earlier report [67JCS(C)1638] in which the 4-isomer was said to dominate. The lower orientation compared with that in nitration has been attributed to steric hindrance to bromination at the (-position [79AHC(24)151]. [Pg.386]

A mixture of iodine with iodine pentafluoride, or bromine with bromine trifluoride, will add iodine monofluoride or bromine monofluoride respectively to fluorinated aUcenes this constitutes a very convenient route to the corresponding monohalopolyfluoroatkanes [178, 179], which is of considerable importance to the surfactant business (Figure 2.30). CIF3, 240°C... [Pg.41]

Aromatic bromides (3, 286). The definitive paper on electrophilic aromatic bromination with bromine and thallium(lll) acetate has been published. The two most oul.standingfeaturc.s are I) monobromination is observed in almost all cases, and 2) exclusive para substitution is observed with almost all monosubstituted benzenes. Electron-withdrawing groups inhibit bromination of monosubstituted benzenes. It... [Pg.492]

Similarly to other purine ribonucleosides, isoguanosine can be brominated with bromine in acetic acid to give 8-bromoisoguanosine (10) bromination in buffered aqueous medium, which has been used in the case of adenosine or guanosine, is not successful due to oxidation. ... [Pg.408]

Regioselective Bromination with Bromine Adsorbed on Zeolite... [Pg.260]


See other pages where Bromination with bromine is mentioned: [Pg.234]    [Pg.55]    [Pg.156]    [Pg.255]    [Pg.293]    [Pg.420]    [Pg.72]    [Pg.1071]    [Pg.315]    [Pg.330]    [Pg.577]    [Pg.189]    [Pg.281]    [Pg.427]    [Pg.226]    [Pg.256]    [Pg.498]    [Pg.185]    [Pg.176]    [Pg.490]    [Pg.39]    [Pg.540]    [Pg.122]    [Pg.293]    [Pg.97]    [Pg.701]   
See also in sourсe #XX -- [ Pg.97 , Pg.116 ]




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2 pyridine, reaction with bromine

2- Allyloxyquinolines, cyclisation treatment with bromine

2-Bromination with cyanogen bromide

2-Butyne, 1,4-dichlororeaction with bromine

2.4.4.6- Tetrabromo-2,5-cyclohexadienone bromination with

3-Chlorocyclobutanecarboxylic acid with mercuric oxide and bromine

4-Ethynyl-l,3-dimethylpyrazole reaction with bromine

Acetals reaction with bromine

Acetate silver, reaction with bromine

Activation with bromine compounds

Adenine activation with bromine

Alcohols, primary with bromine

Alcohols, reaction with bromine

Alcohols, secondary, conversion into with bromine

Aldehydes reaction with bromine

Alkanes, Cycloalkanes and Related Compounds with Chlorine, Bromine, or Iodine Substituents

Alkenes react with bromine

Alkenes reaction with bromine

Alkenes, radical halogenation reactivity with bromine

Alkenes, reaction with aqueous bromine

Alkynes reaction with bromine

Aminotetrazoles, with bromine

Anions reaction with bromine

Anti selectivity, bromine addition with

Benzene derivatives reaction with bromine

Bromide aluminum reaction with bromine

Bromination with NBS

Bromination with hydroxy groups

Bromination with pyridinium tribromide

Bromination with sodium hypochlorite

Bromination-Desilicobromination, with Inversion of Stereochemistry

Brominations with Phosphorus Bromides and Other Reagents

Bromine addition reactions with

Bromine addition with anti stereoselectivity

Bromine amperometric titrations with

Bromine atoms, reaction with

Bromine complex compounds cations, with pyridine

Bromine fluoride reaction with alkenes

Bromine fluoride reaction with oxides

Bromine mixing time with

Bromine olefins with

Bromine radical halogenation with

Bromine reaction with alkanes

Bromine reaction with alkyls

Bromine reaction with amides

Bromine reaction with benzenes

Bromine reaction with dienes

Bromine reaction with enolates

Bromine reaction with enols

Bromine reaction with heterocycles

Bromine reaction with ketones

Bromine reaction with lactose

Bromine reaction with methane

Bromine reaction with pyrimidines

Bromine reaction with silver carboxylates

Bromine reaction with sodium

Bromine reaction with thiourea

Bromine reaction with vinylsilanes

Bromine vapor, bromination with

Bromine with alcohols

Bromine with aldehydes

Bromine with amides

Bromine with carboxylate ions

Bromine with enol ethers

Bromine with ethane

Bromine with ketones

Bromine with methylcyclohexane

Bromine with organometallic

Bromine with phosphoranes

Bromine with polystyrene

Bromine with silanes

Bromine, elemental reactions with

Bromine, oxidation with

Bromine, reaction with aldehydes compounds

Bromine, reaction with cyclic acetals

Bromine, reaction with ethylene

Bromine, reaction with furan in methanol to yield 2,5-dimethoxy-2,5dihydrofuran

Bromine, reaction with hydrogen

Bromine, reaction with hydrogen nitric oxide

Bromine, reaction with phenylacetylene

Bromine, reaction with y-butyrolactone

Bromine, reaction with y-butyrolactone in presence of red phosphorus

Bromine, with 3-chlorocyclobutanecarboxylic acid and mercuric oxide to give l-bromo-3-chlorocyclobutane

Bromine-catalyzed Aziridination of Olefins with Chloramines

Carbohydrates with bromine

Chloroform, reaction with bromine

Comparisons of Bromination-EDXA with Other Methods

Compounding with bromine

Cyclohexene, bromination reaction with Z-butyl perbenzoate and

Cytosine activation with bromine

Dehydrogenation of hydrazo compounds with bromine

Dibromoisocyanuric acid bromination with

Double bond reaction with bromine

Enamines with molecular bromine

Ethylene with bromine

Ethylene, reaction with bromine hydrogen

Fluorine bromine with aluminum bromide

Furan, reaction with bromine and methanol to yield 2,5-dimethoxy-2,5-dihydrofuran

Graphite, intercalation compounds with bromine

Guanine activation with bromine

Halogenated Arenes and Carboxylates with Chlorine, Bromine, or Iodine Substituents

Halogenation with bromine vapor/solution

Hydrocarbons reaction with bromine

Hydrogen, reaction with bromine carbon dioxide

Hydrogen, reaction with bromine chlorine

Hydrogen, reaction with bromine iodine

Hydrogen, reaction with bromine nitrous oxide

Hydrogen, reaction with bromine oxygen

Hydrogen, reaction with bromine sulphur

Hydrosilane with bromine

Magnesium, combining with bromine

Mannose reaction with bromine

Mercuric oxide, reaction with bromine

Nitric oxide with bromine

Nitric oxide, decomposition reaction with bromine

Nucleophilic Displacement of Bromine or Chlorine Atoms with the Fluoride Anion

Nucleophilic Displacement of Bromine or Chlorine Atoms with the Fluoride Ion

Organic reactions regioselective bromination with bromine

Oxalic acid, reaction with bromine

Phenol reaction with bromine

Phenols with bromine

Propene reaction with bromine

Pyrazolines oxidation with bromine

Pyridine molecular complex with bromine

Pyridine, 4-benzoyl bromination with

Quinones with bromine

Reaction with bromine

Reaction with bromine(III) fluoride

Red Phosphorus with Bromine

Replacement bromine with hydrogen

Selectivity in Radical Halogenation with Fluorine and Bromine

Silver, reaction with bromine

Singlet oxygen with bromine

Substitution reactions, with bromine

Succinimide selective bromination with

Sulfides, bis reaction with bromine

Sulfur lignin compounding with bromine

Thebaine reaction with bromine

Thiourea with bromine

Titrations with 0.1 N bromine

Triphenylphosphine, adduct with bromine

With Bromine, Iodine or Sulfuryl Chloride

With bromine

With bromine

Zeolites regioselective bromination with bromine

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