Pyridine ring containing

In cases where the substituent on the pyridine ring contains a carbonyl group, a weak band for the C-0 stretch can be detected in the SERS spectra, generally near 1700 cm. ... 

The [2,3- ]> [2,3- ]. and [i,Z-b] isomers of 2,3-disubstituted furopyridines can be obtained from alkynes and o-iodoacetoxypyridines by a palladium-catalyzed cross-coupling reaction followed by an electrophilic iodocyclization reaction or a palladium-catalyzed cyclization in the presence of CO, as illustrated in Scheme 32 for [2,3-3] and [3,2-3] derivatives. When the pyridine ring contains strongly electron-withdrawing substituents such as carboethoxy, the reaction proceeded smoothly with benzyloxyalkynylpyridines <20020L2409>. 

Pyridine rings containing electron-donating substituents are deactivated toward the Chichibabin reaction relative to pyridine. Pozharskii et al. have studied the amination of the three isomeric aminopyridines. Treatment of an aminopyridine results in evolution of ammonia and formation of the sodium salt of the heterocycle. The sodium salt of 2-aminopyridine (88) was readily aminated at 160-180°C, forming 2,6-diaminopyridine (65) in 70-80% yield. 

The isolation of piercidine A and piercidine B from Strepiomyces mobaraensis cultures, obtained from soil samples, is also linked with the name of Tamura and coworkers (Tamura et al., 1963 Takahashi et al., 1965 1967 Suzuki et al., 1966 Yoshida et al., 1977). Piercidine A (62) has a pyridine ring containing several substituents including an unsaturated side chain with seventeen carbon atoms. Piercidine B (63) contains a methoxy substituent instead of a hydroxy group at carbon atom 10 of the side chain. 

NaBH4 does not react with pyridine. However, if the pyridine ring contains electron-attracting substituents, reduction with NaBH4 leads to di- and tetrahydropyridines. 3-Cyanopyridine, for instance, yields 120 and 121 ... 

When the alkyl side chain attached to a pyridine ring contains three or more carbons arranged linearly, fragmentation via the McLafferty rearrangement can also occur. 

Thermally stable POD films containing pyridine rings have potential appHcation as reverse osmosis membranes (58). 

However, five-membered rings containing two or more heteroatoms necessarily possess both a pyridine-like heteroatom and a pyrrole-like heteroatom. Thus their chemistry shows similarities to both those of the six-membered rings and of the five-membered rings with one heteroatom this is dealt with in Part 4. 

The //NMR spectrum contains five signals with integral levels in the ratios 1 1 1 1 3 four lie in the shift range appropriate for aromaties or heteroaromaties and the fifth is evidently a methyl group. The large shift values (up to Sh = 9.18, aromaties) and typical coupling constants (8 and 5 Hz) indicate a pyridine ring, which accounts for four out of the total five double-bond equivalents. 

These intramolecular IHDA pyrimidine-to-pyridine ring transformations are also successfully applied to synthesize bicyclic heterocycles, containing a... 

A thioamide of isonicotinic acid has also shown tuberculostatic activity in the clinic. The additional substitution on the pyridine ring precludes its preparation from simple starting materials. Reaction of ethyl methyl ketone with ethyl oxalate leads to the ester-diketone, 12 (shown as its enol). Condensation of this with cyanoacetamide gives the substituted pyridone, 13, which contains both the ethyl and carboxyl groups in the desired position. The nitrile group is then excised by means of decarboxylative hydrolysis. Treatment of the pyridone (14) with phosphorus oxychloride converts that compound (after exposure to ethanol to take the acid chloride to the ester) to the chloro-pyridine, 15. The halogen is then removed by catalytic reduction (16). The ester at the 4 position is converted to the desired functionality by successive conversion to the amide (17), dehydration to the nitrile (18), and finally addition of hydrogen sulfide. There is thus obtained ethionamide (19)... 

Heterocycle (Sections 15.5, 24.9) A cyclic molecule w hose ring contains more than one kind of atom. l or example, pyridine is a heterocycle that contains five carbon atoms and one nitrogen atom in its ring. 

Coordination compounds containing bidentate ligands are often thermally more stable than those comprised of related monodentate ligands, e.g. ethylenediamine (en) complexes dissociate at a higher temperature than those of ammonia or pyridine. Compounds containing a ring structure, such as coordinated salicylaldehyde (sal) and acetyl-acetonate (acac), are particularly stable, and may often be sublimed... 

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