Bromination aldehydes

Another method of aldehyde bromination, apart from Riehl s established method (432) from bromine at 20°C, is to use trimethylphenyl-ammonium bromide in tetrahydrofuran solution, prepared by Vorlander and Siebert s method (50). However, the yield of 5-phenylthiazole using this method with thioformamide dissolved in dioxane is only 8% (513). 

Thiophene-2-carbaldehyde, 3-bromo-synthesis, 4, 81 Thiophenecarbaldehydes benzothiophene synthesis from, 4, 906 reactions, 4, 807 synthesis, 4, 148 Wittig reactions, 4, 807 Thiophene-2-carb aldehydes bromination, 4, 753 conformation, 4, 33 halogenation, 4, 753 reactions, 4, 72-73 reactivity, 4, 72-73 reduction, 4, 776 Thiophene-3-carb aldehydes conformation, 4, 33 reactivity, 4, 72... 

Finally, in 1979 Florton reported the synthesis of 3-amino-2,3-dideoxyhexu-ronic acids. In six steps, methyl a-D-maimopyranoside was converted to a highly functionalized 3-acetamido-6-azido-2,3,6-trideoxy derivative. Photochemical activation of the azide provided an imine, which was subsequently hydrolyzed to the aldehyde. Bromine was used to oxidize the aldehyde to the acid, which was esterified with methyl iodide (Fig. 9). 

ETHYL ACETONE (107-87-9) Forms explosive mixture with air (flash point 45°F/7°C). Reacts violently with strong oxidizers, aldehydes, bromine trifluoride, hydrogen peroxide, nitric acid, perchloric acid. Attacks some plastics, rubber, and coatings. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

Asaronealdehyde (2,4,5-trimethoxy-benzaldehyde) can be produced in the following way Methylate resorcinol. Product is 1,3-di-MeO-benzene. Do a Vilsmeyer aldehyde synthesis with POCI3/N-methylformanilide to obtain 2,4-di-MeO-benzaldehyde. Brominate and treat as described above to obtain asaronaldehyde. 

Syntheses of a,)3-dihalogenoethers can be achieved in various ways the classical method (37), wherein a current of dry gaseous hydrochloric acid, is made to react in an equimolar mixture of ethanol and aldehyde at 20°C first to form the monochloroether (50% yield) and then by the action of bromine, the dibromoether (80 to 90% yield) can be used. The second and simpler method is the direct bromination of ethylvinylether in a chloroformic or dioxane solution if the product is used directly without purification,... 

Aminolhtazoles were synthetized from thiourea by three methods Method A, from a-haloketones or aldehydes designated as (Cl) or (Br) Method B, from ketones and iodine (fj) or bromine (Btj) Method C, from iodomercuriketones. Method D consists in condensing ketones with cyanamid and sulfur. 

Derivatives of aldoses in which the terminal aldehyde function is oxidized to a car boxylic acid are called aldonic acids Aldonic acids are named by replacing the ose ending of the aldose by omc acid Oxidation of aldoses with bromine is the most com monly used method for the preparation of aldonic acids and involves the furanose or pyranose form of the carbohydrate... 

When a preparative method for an aldonic acid is re quired bromine oxidation is used The aldonic acid is formed as its lactone More properly described as a reaction of the anomeric hy droxyl group than of a free aldehyde... 

Bromination of aldehydes (qv) is more compHcated because bromination can take place on the aldehyde carbon as weU as the a-carbon. Acetals are brominated satisfactorily in cold chloroform solution in the presence of calcium carbonate, which reacts with the hydrogen bromide formed (24). 

Acids and esters (see Esters, organic) are less easily brominated than aldehydes or ketones. Acid chlorides and anhydrides are more easily brominated (23). 

Aldehydes can be dkeedy converted to esters using bromine in alcohol solvents with sodium bicarbonate buffer (41). 

V-bromosuccinimide [128-08-5] C H BrNOj 180-183 2.098 brominating olefins, oxidizing alcohols to aldehydes and ketones, converting aldehydes to acid bromides... 

Excess of bromine converts each methylpteridine compound into the dibromomethyl derivative which on hydrolysis gives good yields of the corresponding aldehyde. An interesting variation of the reaction conditions was found in the treatment of the C- methylpteridines with POBra, which leads to the same mono- and di-bromomethyl derivatives. 6-Methylpterin reacts with more difficulty and with an excess of bromine in hydrobromic acid forms the... 

We present here examples of this condensation with an aromatic aldehyde and a cyclic ketone. Both of these examples are useful because, although other methods are available for their preparation, problems often attend these syntheses. In the synthesis of cyclohexy11deneaceton1tr11e, for example, the standard method results exclusively In the g.y-lsomer and none of the a,g-Isomer. In Part A of this procedure, cyclohexanone Is condensed with acetonitrile to give predominantly the conjugated Isomer (80-83%) whicfi is then separated from the nonconjugated isomer by selective bromination. 

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