Benzoylation reaction

The benzoylation reaction was applied to cyclic enamines (384) and the synthesis of a heptazulene (385). 

There was some dispute over the product resulting from the benzoylation reaction of amide 266, which, according to the original investigators, has the furazan stmcture 267 (Scheme 172) (29LA54). 

The reaction is less selective than the related benzoylation reaction (/pMe = 30.2, cf. 626), thereby indicating a greater charge on the electrophile this is in complete agreement with the greater ease of nuclophilic substitution of sulphonic acids and derivatives compared to carboxylic acids and derivatives and may be rationalized from a consideration of resonance structures. The effect of substituents on the reactivity of the sulphonyl chloride follows from the effect of stabilizing the aryl-sulphonium ion formed in the ionisation step (81) or from the effect on the preequilibrium step (79). 

Benzoylation reactions of phenols (33, 97) and naphthols (20, 98-100) can be accomplished very efficiently by heating with benzoyl chloride (101) under-... 

Specifically, in reactions of 4 with acetic anhydride in the presence of zinc chloride58 or boron trifluoride17,35 as the catalyst, 1,2,5-tri-O-acetyl-/J-D-glucofuranurono-6,3-lactone (12) is the preponderant product in the presence of pyridine,58 however, acetylation of 4 by acetic anhydride leads to the favored formation of the corresponding a-D anomer. In contrast to acetylations, in benzoylation reactions, the ratio of anomers apparently changes. Thus, on treatment of 4 with benzoyl chloride in pyridine, Momose and coworkers17 isolated... 

Acetyl or benzoyl groups can be introduced into the 5-position of dihydropyrrolo[2,3-. ]pyridinones via a palladium-catalyzed reaction. The acetylation proceeds in much higher yields than the benzoylation reaction (Scheme 5) <1997T5159>. 

The monomers described so far have all been prepared by starting with 4-bromobenzocyclobutene, 2. A different approach to the preparation of monomers begins with the parent hydrocarbon benzocyclobutene 1 by carrying out electrophilic aromatic substitution reactions [36]. Benzocyclobutene readily undergoes a Friedel-Crafts benzoylation reaction with a variety of substituted acid chlorides (Fig. 7). 

Note. (1) A mixture of anomeric glucose pentabenzoates such as might be obtained from a benzoylation reaction on glucose without careful temperature control gives equally good results. 

An attempt has been made to analyse whether the electrophilicity index is a reliable descriptor of the kinetic behaviour. Relative experimental rates of Friedel-Crafts benzylation, acetylation, and benzoylation reactions were found to correlate well with the corresponding calculated electrophilicity values. In the case of chlorination of various substituted ethylenes and nitration of toluene and chlorobenzene, the correlation was generally poor but somewhat better in the case of the experimental and the calculated activation energies for selected Markovnikov and anti-Markovnikov addition reactions. Reaction electrophilicity, local electrophilicity, and activation hardness were used together to provide a transparent picture of reaction rates and also the orientation of aromatic electrophilic substitution reactions. Ambiguity in the definition of the electrophilicity was highlighted.15... 

The importance of the steric effect accounts for the spread of the data for lf-N in the substitution reactions. Nitration and non-catalytic chlorination, reactions of modest steric requirements, define points which fall above the arbitrary reference line. Bromination, a reaction of somewhat greater steric requirements, is not accelerated to the extent anticipated on the basis of the results for nitration or chlorination. The benzoylation reaction with large steric requirements is two orders of magnitude slower than the equally selective chlorination reaction. The unusually small ratio for lf-N/2f-N for the acylation reaction is a further indication of the steric effects. Apparently, the direct substitution reactions of naphthalene respond to the retarding steric influence of the peri hydrogen in much the same way as for other ortho substituents. 

Scheme 4.1 Benzoylation reaction of anisole with benzoic anhydride.

Among all the benzoylation reactions of substituted benzene derivatives, the phenol reaction is interesting to consider and to develop due to the fact that it may occur... 

Benzoylation of benzene and other aromatic compounds by benzoyl chloride over H-BEA zeolite modified by indium oxides has been investigated.191 We report in Table 4.2 the time required for half reaction (L/2) f°r a series of aromatic substrates used in the above reaction. The benzoylation reaction rate (via L /2 value) depends strongly on the substituent group present in the aromatic substrate and increases due to the presence of the electron-donating group, depending upon its electron-donating ability. The activity order is as follows benzene toluene < p-xylene < anisole. 

The liquid phase benzoylation reactions over HBEA zeolite catalyst were operated under nitrogen to minimize the hydrolysis of acylating agent in a magnetically stirred glass reactor equipped with a condenser and a dropping funnel. 

Figure 4.2 Hammett relationship (log 11/2 versus a) in the benzoylation reaction of benzene and substituted aromatic compounds with benzoyl chloride over H-BEA zeolite modified by indium oxides...

Benzo(6]thiophene halogenation, 57, 294 iodination, 59, 254 resonance energy, 56, 352 Ru, Ir complexes, 58, 150 Benzo[6]thiophene, 3-benzoyl-, reaction with hydrazine, 56, 128 Benzo[l)]thiophene, 3-bromo-, chlorination, 57, 293 Benzo[6]thiophene, 4-fluoro-, 60, 17 Benzo[/>)thiophene, 4,5,6,7-tetrafluoro-2,3-dihydro-2-methyl-, 60, 28 Benzo(e]thiophenes, resonance energy,... 

The starting 733 could be prepared from the D-glucose derivative 730 by benzoylation to 731, followed by partial deisopropylidenation to 732 and then periodate oxidation, reduction, and tosylation. Alternatively, it was formed from the D-xylose derivative 735 by partial hydrolysis to 734, followed by tosylation and then benzoylation. Reaction of 733 with the sodium salt of bases gave 736. Hydrolysis of the isopropylidene group followed by periodate oxidation, reduction, and then debenzoylation gave 737 (79CCC593). 

The benzoylation reaction must be carried in an ice-bath and at no stage the temperature of the reaction mixture be allowed to go beyond 5-8°C. 

This is not a direct benzoylation reaction, but benzyl benzoate may be prepared by the interaction of freshly distilled benzaldehyde with sodium benzylate. It is an exothermic reaction and the temperature of the reaction mixture should be maintained between 50-60°C. The final product is obtained by distillation rmder reduced pressure and the distillate collected at 184-185°C/15 mm pressure. 

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