Pyridine Derivatives and Related Compounds

PYRIDINE DERIVATIVES AND RELATED COMPOUNDS (BENZOPYRIDINES = QUINOLINES)... 

For sake of completeness it should be mentioned a carboxylic acid hydrazide, namely pyridine-4-carboxylic acid hydrazide (isonicotinic acid hydrazide, Isoniazide), a pyridine derivative which is appropriately described under 13. Pyridine Derivatives and Related Compounds (see 13.2.). 

Pyridine Derivatives and Related Compounds (Benzopyridines = Quinolines)... 

Yoneda, R., Terada, T., Harusawa, S., and Kurihara, T., Studies on indenopyridine derivatives and related compounds. Part 4. Synthesis and stereochemistry of ethyl 9,9-dimethyl-l,2,3,9a-tetrahydro-9/7-indeno[2,l-fc]pyridine-3-carboxylate and its derivatives. Heterocycles, 23, 557, 1985. 

H-Thiopyrans may occasionally be isolated from the reaction of 1,5-diketones, hydrogen sulphide, and acids, although they usually disproportionate under these conditions. Dienones give 2 T-thiopyrans with the same reagents. " [4 + 2] Cycloaddition of 3-dialkylaminovinyl aryl thiones with acrylic acid derivatives and related compounds afforded the 2fT-thiopyrans (10 R = H, OEt R = CN, CONHg, COMe, etc.). The intermediate 4-dialkylamino-A -dihydrothiopyrans were sometimes isolated. Factors affecting the addition were studied, and some reactions of (10) and the derived thiopyrylium salts were described. The preparation of the azido-thiopyrans (11 R = H or Ph) by the action of sodium azide on the thiopyrylium salts has been reported. Their thermolysis afforded substituted pyridines, thiophens, and sulphur, which were the decomposition products of the expected thiazepine intermediates. 

Pyrans and related compounds react with ammonia to give pyridines. A commercially useful example is the reaction of dehydroacetic acid (derived from diketene) with ammonia to give 2,6-dimethyl-4-pyridinone [7516-31 -6] via 2,6-dimethyl-4-pyridinone-3-carboxyhc acid [52403-25-5]. Chlorination of the pyridone gives clopidol [2971-90-6] (56), a coccidiostat (72,73). 

The most common reaction of this type is the cyclization of various derivatives of hydrazine and substituted hydrazines with pyridine o-dicarboxylic acids and related compounds. Reactions in which the acid derivative reacts directly with the hydrazine are dealt with as [4 + 2] reactions in Section 2.15.10.6.1. 

Finally, the formation of derivatives of pyridine from 5-hydroxymethylfurfural and related compounds on treatment with ammonia 0 may be considered in this section on the furan ring. 5-Hydroxymethyl-furfural itself gives 2-hydroxymethyl-5-hydroxypyridine (XLIV) with ammonia, which is presumably formed by opening of the ring in the intermediate aldehyde-ammonia compound followed by closure to give the 6-membered ring. 

Pyridine derivatives containing sulfur. XXXIV. Synthesis of 2-AlkyI-mercapto-5-chloro (and ethoxy) pyrido[3.2-d] thiazole and related compounds. J. Pharm. Soc. Japan 71, 920 (1951) Chem. Abstracts 46, 8110 (1952). 

The formation of pyridine IV-imines by an add-catalyzed rearrangement of some diazepinones and related compounds has been extensively investigated by Moore and co-workers (Eq. 9).115 The formation of pyridine N-imines from l/f-l,2-diazepines is also known (Eq. 10).68 69,116,117 Diels-Alder reactions of pyrazoles with dimethyl acetylenedicarboxylate, in the presence of BF3, have been reported to give IV-aminopyridinium salts (Eq. II).118 l,4-Dihydropyrido[l,2-a]-as-triazinium salts and their pyrimido derivatives undergo ring contraction in boiling aqueous acid, yielding 1-aminoimidazo[l,2-a]pyridinium and pyrimidinium salts, respectively (Eq. 

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