Benzylic bromides, reaction

Benzyl-6-methylcyclohexanone has been prepared by the hydrogenation of 2-benzylidene-6-methylcyclohexanone over a platinum or nickel catalyst, and by the alkylation of the sodium enolate of 2-formyl-6-methylcyclohexanone with benzyl iodide followed by cleavage of the formyl group with aqueous base. The 2,6-isomer was also obtained as a minor product (about 10% of the monoalkylated product) along with the major product, 2-benzyl-2-methylcyclohexanone by successive treatment of 2-methylcyclohexanone with sodium amide and then with benzyl chloride or benzyl bromide. Reaction of the sodium enolate of 2-formyl-6-methylcyclohexanone with potassium amide in liquid ammonia formed the corresponding dianion which was first treated with 1 equiv. of benzyl chloride and then deformylated with aqueous base to form 2-benzyl-2-methylcyclohexanone.i ... 

MA in synthesis, 227 Triphenylphosphine-MA adduct benzyl bromide reaction, 231 n-butylraldehyde reaction, 231 Triplet excitation energies, photosensitizers, 185 Tripropylamine, 7... 

Alkvl Azides from Alkyl Bromides and Sodium Azide General procedure for the synthesis of alkyl azides. In a typical experiment, benzyl bromide (360 mg, 2.1 mmol) in petroleum ether (3 mL) and sodium azide (180 mg, 2.76 mmol) in water (3 mL) are admixed in a round-bottomed flask. To this stirred solution, pillared clay (100 mg) is added and the reaction mixture is refluxed with constant stirring at 90-100 C until all the starting material is consumed, as obsen/ed by thin layer chromatographv using pure hexane as solvent. The reaction is quenched with water and the product extracted into ether. The ether extracts are washed with water and the organic layer dried over sodium sulfate. The removal of solvent under reduced pressure affords the pure alkyl azides as confirmed by the spectral analysis. ... 

Benzyl bromide can be converted into ethylbenzene (731) by the reaction of Me4Sn. The use of HMPA as a solvent is important. Overall inversion of configuration takes place at the chiral center of deuterated benzyl bro-mide[598]. The cyanomethyiation[599] and methoxymethyiation[600] of aromatic rings are carried out by the reaction of cyanomethyltributyltin (732) and methoxymethyltributyltin. 

The sulfur atom of the thiocarbonyl group is a good nucleophile, and reaction between benzyl bromide and l-(2-thiazolyl)thiourea yields the isothiouronium salt (496). The sulfur atom may also be engaged in a chelate, as exemplified by the Cu chelate of 2-thioureido-4-methylthiazole (491). These chelates with metal ions were thoroughly studied in acidic, neutral, and alkaline media for 66 metal ions in order to define their analytical use. They are formed in the molar ratio of 1 2 for metal II compounds (498). 

Solvent Preparation. The most critical aspect of the solvent is that it must be dry (less than 0.02 wt % of H2O) and free of O2. If the H2O content is above 0.02 wt %, then the reaction of Mg and RX does not initiate, except for an extremely reactive RX species, such as benzyl bromide. Although adventitious O2 does not retard the initiation process, the O2 reacts with the Grignard reagent to form a RMg02X species. Furthermore, upon hydrolysis, the oxidized Grignard reagent forms a ROH species that may cause purification problems. 

Treatment of 3-hydroxy-l,2-benzisoxazole with benzyl bromide gave a mixture of O-and iV-benzyl compounds. The iV-benzyl compound gave a benzoxazin-4-one on reaction with base, via the intermediates shown in Scheme 88 (78CPB549). 

N Alkylation of 16 with benzyl bromide also occurs, and further heating of the reaction mixture leads to the C-alkylated product (25), probably by an intermolecular mechanism (33). 

Since cbiral sulfur ylides racemize rapidly, they are generally prepared in situ from chiral sulfides and halides. The first example of asymmetric epoxidation was reported in 1989, using camphor-derived chiral sulfonium ylides with moderate yields and ee (< 41%) Since then, much effort has been made in tbe asymmetric epoxidation using sucb a strategy without a significant breakthrough. In one example, the reaction between benzaldehyde and benzyl bromide in the presence of one equivalent of camphor-derived sulfide 47 furnished epoxide 48 in high diastereoselectivity (trans cis = 96 4) with moderate enantioselectivity in the case of the trans isomer (56% ee). ... 

Interestingly, a reverse isomerization (1,4-dihydro 1,2-dihydro) was observed when a 1,4-dihydroquinoline derivative was obtained by the reaction of lithiated l-ethoxycarbonyl-l,2-dihydroquinoline-2-phosphonate 36 with benzyl bromide... 

Preparation of 1,3-Diphenyl-2,2-Dimethylpropanone-1 Sodamide was prepared from 12.5 grams of sodium added in small portions to 600 cc of liquid ammonia with 1 gram of hydrous ferric chloride as catalyst. The ammonia was replaced by 200 cc of dry toluene and without delay a solution of 74 grams of isobutyrophenone and 76.5 grams of benzyl bromide in 200 cc of benzene was slowly added with stirring. The reaction mixture was heated on a boiling water bath for 48 hours. Water was then added, the organic layer separated and the product isolated by distillation. The 1,3-diphenyl-2,2-dimethylpropanone-1 boiled from 142°-143°C at a pressure of 3 mm, t ° 1.5652. 

The alkylation of sodium 2-naphthoxide with benzyl bromide in tetrabutylam-monium and tetrabutylphosphonium halide salts was investigated by Brunet and Badri [50] (Scheme 5.1-21). The yields in this reaction were quantitative, and alkylation occurred predominantly on the oxygen atom of the naphthoxide ion (typically 93-97 %). The rate of the reaction was slower in the chloride salts, due to the benzyl bromide reacting with chloride ion to give the less reactive benzyl chloride. 

The synthesis of halodeoxy sugars has also been achieved by reaction of sugar phosphorodiamido and phosphonamido derivatives with alkyl halides (83). Heating equimolar amounts of 6-(tetraethylphosphoro-diamido)-l,2 3,4-di-0 isopropylidene-D-galactose with methyl iodide (and benzyl bromide) at 140°C. for 4 hours afforded the 6-deoxy-6-iodo (74b) (75%) and 6-bromo-6-deoxy (74c) (56%) derivatives, respectively. 

Benzyl bromide is converted into benzaldehyde by heating in dimethyl sulfoxide. Propose a structure for the intermediate, and show the mechanisms of the two steps in the reaction. 

The authors have also elaborated a microwave-enhanced one-pot procedure [90] for the Huisgen 1,3-dipolar cycloaddition reaction. In a typical procedure, a pyrazinone with a triple bond connected to the core via C - O linkage, was reacted with a suitable benzylic bromide and NaNs in presence of the Cu(I) catalyst in a t Bu0H/H20 system under microwave irradiation (Scheme 26). The cycloaddition was found to proceed cleanly and with full regioselectivity. As the azide is generated in situ, this procedure avoids the isolation and purification of hazardous azides, which is especially important when handling the ahphatic ones, which are known to be toxic and explosive in nature. 

For instance, bromination of toluene in carbon tetrachloride did not proceed at reflux, even though pentamethylbenzene was brominated at 30°C to give bromopentamethylbenzene quantitatively. Toluene and copper(II) bromide reacted at reflux for 72 h. to give benzyl bromide as the main product. In a similar reaction with alumina-supported copper(II) bromide, bromotoluene (o/p = l) was obtained in good yield and no side-chain-brominated compounds were detected. 

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