الفهرس 
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Abstract
SUMMARY
It has been found that 4-hydroxy - 6 - methyl - 2 - pyridone 1 reacts with arylidine derivatives 2a-e in alcoholic solution containing catalytic amount of piperidine to yield 5. The formation of 5 was demonstrated in chart No. 1. When 1 was subjected to react with 2 f-h, in pyridine, compound 7 was obtained .
The pyridones 1 reacts with an equimolecular amount of 9a in ethanol catalyzed with a few DROPs of piperidine to give a new spiro compound 12 .
In contrast to the behaviour of 9a , compmmd 9b was reacted with 1 under the same reaction conditions to yield the 2-amino-quinoline - 3 0carbonitriles 14 . It is assumed that 14 would be formed through an intramolecular cyclization of the intermediate 13 which was derived from 9b through ring opening (cf. chart 2).
The reaction of arylmethylenecyanothioacetamides 16a-c with 1 in ethanol catalyzed with triethylamine afford the bis (4- hydroxy - 6 - methyl . 2 - oxo - 2(1H) - 3 - pyridinyl) arylmethanes 21a-c instead of the expected pyrano [3, 2 - c] pyridines 17. Compmmds 21a-c could be independently synthesised via reaction of 1 with the corresponding aromatic aldehyde .
Pyrano [3, 2 - c] pyridines 5 a, f were subjected to further reactions.
Thus, compound 5a reacts with acetic anhydride to yield two products
(22 and 23). While reaction of 5f with acetic anhydride afforded only the exocylic amines acetylation product 24 .
In an attempt to obtain the desired pyrimidine derivative 25. We firstly tried the reaction of 5a, f with phenylisothiocyanate under reflux in benzene ; dioxane or toluene / TEA, for extended periods. However, the expected reaction did not proceed and the starting materials were recovered. Then, I repeated the reaction in a solvent of higher boiling point as N, N-dimethylfonnamide. When 5 a,f and phenylisothiocyanate were refluxed in DMF for 8 hrs. Also failed to yield 25, instead forming the unexpected product which shown to be same as the product obtained from the reaction of 1 with 16a ; viz. product 21a ; by its m.p.s. and spectral data . A mechanistic proposal for the formation of this product 21 a involves the nucleophilic attack of H20 (probably present in solvent) on the pyran ring to form the ring-opend intermediate 26. Then, the mechanism steps proceeded similar to that discussed above for the formation of 21 from 1 and 16 (cf. Chart 5). On the other hand, when compOlmds 5a,f were heated in boiling DMF and in the absence of PhNCS, the product 21a was also obtained. To our knowledge, this is the first repoted conversion of pyrano [3 ,2-c] pyridines into bis (4methyl-2-oxo-2(1H)-3-pyridinyl)- aryl methanes. The results indicate that 4- hydroxy -2 - pyridones 1 is excellent starting material for the synthesis of heterocyclic compounds which are not otherwise readily accessible.