Dibenzo Pyridine

Chemical Designations - Synonyms 10-Azaanthracene, Benzo (b) Quinoline, Dibenzo [b,e] Pyridine Chemical Formula C,3H,N. 

Chloro-5-nitrobenzaldehyde, -acetophenone, or -benzophenone derivatives treated with 2-aminothiophenol under alkaline conditions provided good yields of the corresponding dibenzo[(3,/][l,4]thiepins. Similar treatment of 2-chloro-3,5-dinitrobenzophenone (318) provided 58% of dibenzo[(3,/][l,4]thiepin 321 and 20% of phenothiazine 323. Its formation can be easily explain by the Smiles rearrangement of the initially formed intermediate 320 into diphenylamine derivative 322, followed by denitrocyclization reaction leading to the corresponding product of denitrocyclization 323 (Scheme 49). When the reaction was done in pyridine, only this product was isolated in 50% yield (57JCS3818). 

Scheme 5. Selective removal of the dibenzo[18]crown-6 methyl ether, pyridine, CH2CI2, 20 °C, 14 H 68 % from tether from conjugate ( )-24. a) TsOH, toluene, A, 3 h. b) ( )-24.

The arylation of potassium phenoxide has been studied by Litvak and Shein (1976). In the absence of crown ether the rate of reaction with p-nitrobromobenzene in various solvents increases in the order dioxan < methanol < pyridine < DMSO. In the presence of either 18-crown-6 [3] or dibenzo-18-crown-6 [11], the order of the reaction rates in dioxan and methanol is reversed (Table 22). The effect of crown ether addition on the rate... 

Figure 5.8 Three recognition motifs based on (a) hydrogen bonding interactions between 2,6-diaminopyridine and thymine, (b) metal coordination of suUur-carbon-sulfur (SCS) Pd pincer with pyridine, (c) pseudorotaxane formation between dibenzo[24]crovvn-8 (DB24C8) and dibenzylammonium ions, and (d) fuUy functionaUzed terpolymer 5.

In a reinvestigation of earlier work (33LA(505)103) by Diels and Alder, Acheson et al. (60JCS1691) established that the stable isomer obtained by addition of two moles of dimethyl acetylenedicarboxylate to one of pyridine was the 4/7-quinolizine (96) and that this with bromine was oxidized to a quinolizinium salt (97 Scheme 65). 4iT-Quinolizines obtained from isoquinoline (62JCS748) and phenanthridine (63JCS3888) were similarly aromatized to afford benzo[a]quinolizinium (98) and dibenzo[a,c]quinolizinium ions (99) respectively. 

A less obvious instance is the acylation of l,5-anhydro-4,6-0-benzylidene-D-glucitol. The 1,5-anhydride has a chair conformation, and the 2- and 3-hydroxyl groups are equatorially attached trans to each other, and are, apparently, essentially equivalent91 However, the 2-benzoate and 2-p-toluenesulfonate were obtained almost exclusively on using the acyl chlorides in pyridine, although in the former acylation, an appreciable proportion of the dibenzoate was formed. 

A number of monocyclic and benzo-annelated examples of 1,2- and 1,3-thiazepines have been prepared but there has been little systematic study of these systems. The interesting photochemical interconversions of pyridine N-imides into 1,2- and 1,3-diazepines and of pyridine Af-oxides into 1,2- and 1,3-oxazepines regrettably lack parallels in thiazepine chemistry. There has been more interest in 1,4-thiazepines, as both rearrangement products and possible biogenetic precursors for penicillins and because of the pharmacological value of the benzo- and dibenzo-[l,4]thiazepines as antidepressants and coronary vasodilators. The only review (70ZC361) is excellent but not very recent. 

Dibasic Calcium Phosphate Dibenzo (B,E) Pyridine Dibenzoyl Peroxide DIBK... 

ACRIDINE Dibenzo [ b,e] Pyridine, lti-Azaanthracene, Benzo(b)-Qni noline Poison, III NL NL NL ... 

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 dibenzoylation64 of methyl a-L-fucopyranoside (20) with benzoyl chloride-pyridine at a low temperature gave the amorphous 2,3-dibenzoate in high yield (80-85%) methyl 3-O-benzoyl-a-L-fuco-pyranoside was also isolated, in 6% yield. [Similar treatment of methyl 6-deoxy-a-L-mannopyranoside (a-L-rhamnopyranoside) gave the corresponding 2,3-dibenzoate in 50% yield, although, in this compound,... 

Table III summarizes experimental and theoretical data on the first three absorption bands (Lb, La, Bb) in the spectra of pyridine, quinoline, isoquinoline, acridine, and their benzo and dibenzo derivatives.

Fused benzene rings aid nucleophilic attack on pyridines, pyridinium and pyrylium ions, and pyrones the loss of aromaticity involved in the formation of the initial adduct is less in monobenzo derivatives and still less in linear dibenzo derivatives than in monocyclic compounds. For the same reason, the tendency for this initial adduct to re-aromatize is less for benzopyridines. Fused benzene rings also influence the point of attack by nucleophilic reagents attack rarely occurs on a carbon atom shared with a benzene ring. Thus, in linear dibenzo derivatives, nucleophilic attack is at the y-position (157). 

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