Benzoyl group position

Heating 2-phenyl-4-benzoyl-l,3,4-thiadiazolium chloride (121) at 200 °C causes the benzoyl group to move to the 2-position as in (122) (68AHC(9)165), probably via deprotonation. 

First the five protons (integral) of the //NMR spectrum (Sfj = 7.50 - 7.94) in the chemical shift range appropriate for aromatics indicate a monosubstituted benzene ring with typical coupling constants 8.0 Hz for ortho protons, 1.5 Hz for meta protons.). The chemical shift values especially for the protons which are positioned ortho to the substituent Sn = 7.94) reflect a -M effect. Using the CH COLOC plot it can be established from the correlation signal hclS = 66.AI7.94 that it is a benzoyl group A. 

Relatively few pyridines with substituents other than alkyl groups have so far been examined, and with some of these the reaction has been carried out only in the presence of added solvent. A comparison of the reactivities of these pyridines is therefore difficult. It has, however, been established that the presence of benzoyl groups in the 3- and 4-positions causes a very marked drop in the yields of the corresponding 2,2 -bipyridines. The 3- and 4-benzylpyridines were found to be more reactive but even in the absence of solvent, and in vacuo, 4-benzylpyridine gave only about one-third of the yield of the 2,2 -bipyridine compared with pyridine itself. Ethyl nicotinate in the absence of solvent and under vacuum -- gave a similar yield of biaryl but 4-phenylpyridine was found to be less reactive. 

Carbonyl groups on the side chains also activate the dihalides. These particular dihalides were employed to prepare polyfarylenc ether)s containing pendent benzoyl groups.82 The polymers may be used as a positive photoresist for UV irradiation. 

The first observation of a significant rate enhancement in the alkaline hydrolysis of an ester by a suitably positioned carbonyl group that was related to prior attack of hydroxide at the carbonyl group was made in 1955 (Djerassi and Lippman, 1955). However, in 1962, a more detailed mechanistic pathway was suggested which involved attack by hydroxide at an o-formyl or benzoyl group, followed by intramolecular nucleophilic attack on a benzoate ester (Newman and Hishida, 1962 Bender and Silver, 1962). 

In the course of these studies (Scheme 8), it was found that the benzoyl group can migrate to 3- and 4-position from 2- and 3-position at high temperature. Thus temperature could be... 

A variety of electrophiles can be introduced into the 4-position of 3-arylsydnones by way of 4-lithio intermediates <84CHEC-i(6)365>. The method has been used to introduce several sulfur, selenium, and tellurium electrophiles <86BCJ483, 86BCJ487) and to introduce formyl and acetyl substituents <92MI 403-02). 3-Amino-4-benzoylsydnone, the first example of a sydnone with a primary amino substituent at N-3, was prepared by using this method to introduce the benzoyl group (Scheme 8) <88H(27)1697>. 

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 absolute stereochemistry of broussonetine L (8) was determined by the combination of the benzoate chirality method and the Mosher s method [35-37]. A carbamate (8a) was prepared from broussonetine F (4) by reaction with phenyl chloroformate in tetrahydrofuran-H20 (7 3), and a diacetate (8b) was prepared from 8a with acetic anhydride in pyridine. Finally, a dibenzoate (8c) was obtained by benzoylation of 8b. The CD curve of 8c showed a negative Cotton effect (Ae237 -30.9) and a positive effect (Ae223 +15.9) to confirm a counter-clockwise chirality between two benzoyl groups, Fig. (3) [20]. 

Selective debenzoylation has been shown to occur by Restelli de Labriola and Deulofeu160 in the cleavage of penta-O-benzoylhexonic acid nitriles (LXXXIII) to form O-benzoyl-pentose dibenzamides (LXXXIV) with ammonia. Since tetra-O-benzoyl-L-rhamnonic acid nitrile (LXXXV) yields 5-deoxy-L-arabinose dibenzamide (LXXXVI), the benzoyl group in the Wohl degradation products is assumed to be in the 5 positions of the resulting pentoses. 

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