Toluene-benzene mixtures benzylation

Fig. 5.22. Energy profile of the step of the benzylation of a 1 1 toluene benzene mixture with...

Continuous chlorination of benzene at 30—50°C in the presence of a Lewis acid typically yields 85% monochlorobenzene. Temperatures in the range of 150—190°C favor production of the dichlorobenzene products. The para isomer is produced in a ratio of 2—3 to 1 of the ortho isomer. Other methods of aromatic ring chlorination include use of a mixture of hydrogen chloride and air in the presence of a copper—salt catalyst, or sulfuryl chloride in the presence of aluminum chloride at ambient temperatures. Free-radical chlorination of toluene successively yields benzyl chloride, benzal chloride, and benzotrichloride. Related chlorination agents include sulfuryl chloride, tert-huty hypochlorite, and /V-ch1orosuccinimide which yield benzyl chloride under the influence of light, heat, or radical initiators. 

Miscellaneous Reactions. DDQ promotes the ferrocenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate catalyzed iodina-tion of substituted benzenes with ICl, although it does not itself act as a catalyst. With toluene, a 47 53 mixture of ortho.para iodotoluene is obtained in a yield of 82% with 13% chlorotoluene (67 33 ortho.para) also observed. The role of the DDQ has not yet been elucidated, but it is assumed to effectively inhibit unfavorable radical iodination of toluene to form benzyl iodide. Other monoiodinated aromatic species were also prepared from the corresponding arenes under these conditions, including 4-... 

Fig. 4 Schematic representation of the catalytic solvent free oxidation of benzyl alcohol (overall reaction). Here other products include benzene and benzyl benzoate, typically <3-4%. This overall reaction includes two parallel reactions oxidation of benzyl alcohol to benzaldehye, which further oxidizes to behzoic acid and disproportionation of benzyl alcohol to equimolar mixture of toluene and benzaldehyde.

Esters of low volatility are accesible via several types of esterification. In the case of esters of butyl and amyl alcohols, water is removed as a binary azeotropic mixture with the alcohol. To produce esters of the lower alcohols (methyl, ethyl, propyl), it may be necessary to add a hydrocarbon such as benzene or toluene to increase the amount of distilled water. With high boiling alcohols, ie, benzyl, furfuryl, and P-phenylethyl, an accessory azeotroping Hquid is useful to eliminate the water by distillation. 

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. 

Oxidation of benzene (and also chlorobenzene and toluene) by Mn(III) acetate in glacial acetic acid gives a mixture of products including benzyl acetate (from benzene) indicating an initial attack on the aromatic by CH2C02H . The kinetics and actual rate of disappearance of Mn(III) are the same for CgHs and... 

SYNTHESIS A solution of 0.67 g 5-hydroxyindole (indol-5-ol) in 10 ml dry MeOH was treated with a solution of 0.30 g NaOMe in MeOH, followed by 0.70 g benzyl chloride. The mixture was heated on the steam bath for 0.5 h, and the solvent removed under vacuum. The residue was suspended between H20 and CH2CI2, the organic phase separated and the aqueous phase extracted once with CH2CI2. The combined organics were stripped of solvent under vacuum, and the residue distilled. A colorless fraction came over at 170-190 °C and spontaneously crystallized in the receiver. There was obtained 0.90 g (80%) 5-benzyloxyindole with a mp 81-86 °C which increased, on recrystallization from toluene / hexane, to 94-96 °C. A sample prepared from the decarboxylation of 5-benzyloxyindole-2-carboxylic acid has been reported to have a mp of 102 °C from benzene. 

Sarca and Laali199 have used triflic acid in butylmethylimidazolium hexafluor-ophosphate BMIM][PF6 ionic liquid for the benzylation of various arenes with benzyl alcohol [Eq. (5.76)]. When compared with Yb(OTf)3, triflic acid proved to be a better catalyst showing higher selectivity (less dibenzyl ether byproduct) by exhibiting similar activity (typically complete conversion). Of the isomeric products, para isomers dominate. Experimental observations indicate that dibenzyl ether originates from less complete protonation of benzyl alcohol and, consequently, serves as a competing nucleophile. Both substrate selectivity (kT/kB) and positional selectivity (ortho/para ratio) found in competitive benzylation with a benzene-toluene mixture (1 1 molar ratio) are similar to those determined in earlier studies, indicating that the nature of the electrophile is not affected in the ionic liquid. 

Radical fragmentation of 2-nitrophenyl-azo-trityl resin was studied in the presence of various radical acceptor solvents to elucidate possible radical reaction pathways. When using benzene as solvent, only 2-nitro-bi-phenyl was formed as the product of radical substitution reaction (SNR) in 67% yield. Hydrogen-radical abstraction from the polymer backbone (e.g., from the benzylic units of polystyrene) was completely suppressed. When toluene was used as solvent, a mixture of the following products was obtained nitrobenzene, 4-methyl-2 -nitrobisphenyl, 2-methyl-2 -nitro-bisphenyl, and 3-methyl-2 -nitrobisphenyl (9 9 1 1). In the case of toluene, the nitro-aryl radicals undergo H-abstraction with radical substitution as a competing reaction pathway. These results indicate that H-abstraction... 

Partial benzylation with powdered potassium hydroxide as a base and toluene as a solvent was used some 50 years ago for the preparation of 1,6-anhydro-2,4-0-benzyl-P-D-glucopyranose [79]. Since that time, other solvents, such as benzene [80-82], 1,4-dioxane-toluene mixtures [83, 84], or excess benzyl chloride [82, 85] were used as well, with apparent effects on the regioselectivity. Thus, the axially oriented secondary hydroxyl group of lL-l,2,3,4-tetra-0-benzyl-c/i ro-inositol is more reactive than the equatorial one using benzyl chloride alone (ratio of 79 21), whereas the opposite is true (35 65) in benzene as a solvent [82]. Benzylation of myo-inositol derivatives in the latter solvent was also described [80, 81, 86]. 

Fig. 6.21. Electrochromatographic separation of benzene derivatives on monolithic capillary column prepared by UV initiated polymerization. Conditions capillary column, 100 pm i.d. x 25 cm active length stationary phase poly(butyl methacrylate-co-ethylene dimethaciylate) with 0.3 wt. % 2-acrylamido-2-methyl-l-propanesulfonic acid pore size, 296 nm mobile phase, 75 25 vol./vol mixture of acetonitrile and 5 mmol/L phosphate buffer pH 7 UV detection at 215 nm 25 kV pressure in vials, 0.2 MPa injection, 5 kV for 3 s. Peaks thiourea (1), benzyl alcohol (2), benzaldehyde (3), benzene (4), toluene (5), ethylbenzene (6), propylbenzene (7), butylbenzene (8), and amylbenzene (9).

The reaction of HBpin in toluene in the presence of RhCl P(/-Pr)3 2(N2) (1 mol%) at 140 °C resulted in a mixture of (borylmethyl)benzene (69%) and bis(boryl)methyl benzene (7%), along with several products arising from aromatic C-H borylation (ca. 15%).345 Rhodium-bpy complexes catalyzed the borylation at the benzylic C-H bond.351 Pd/C was found to be a unique catalyst for selective benzylic C-H borylation of alkylbenzenes by B2pin2 or HBpin (Equation (70)).360 Toluene, xylenes, and mesitylene were all viable substrates however, the reaction can be strongly retarded by the presence of heteroatom functionalities such as MeO and F. Ethylbenzene resulted in a 3 1 mixture of pinacol 1-phenylethylboron and 2-phenylethylboron derivatives. 

The two sets of conditions most employed for benzylation of dibutylstannylene acetals are benzyl bromide with cesium fluoride in DMF at room temperature and benzyl bromide with tetrabutylammonium iodide or bromide in toluene or benzene at elevated temperatures. Although there are no examples with careful analysis of the product mixtures where the same substrate has been allowed to react under both sets of conditions with terminal 1,2-diols, examination of Table IX suggests that the latter condi-... 

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