STUDIES WITH POLYFUNCTIONALLY SUBSTITUTED HETEROAROMATICS - NEW ROUTES FOR THE SYNTHESIS OF POLYFUNCTIONALLY SUBSTITUTED PYRIDINES AND 1,2,4-TRIAZOLO[1,5-A]PYRIDINES

The 1-substituted ethylidememalononitriles 1a-c condensed with triethy l orthoformate in refluxing acetic anhydride to yield the dienes 2a-c. On the other hand a mixture of N,N-dimethylfomzamide and triethyl ort hoformate condensed with 1a-d to yield the N, N-dimethylaminopentadien onitriles 2d-g. The pentadienonitriles 2d-g were also formed from the reaction of 1a-d with dimethylformamide dimethylacetal in refluxing ac etic acid. When compounds 1a-e weve treated with dimethylformamide dim ethylacetal in refluxing p-xylene, a mixture of 3,4 and 2e-g was forme d. The reaction of 2a,b with hydrazine hydrate afforded the N-amino-2- iminopyridines 5a,b. These were converted into the triazolo[1,5-a]pyri dines 8a-d on treatment with benzoyl chloride and with dimethylformami de dimethylacetal. On the other hand, the reaction of 2c with hydrazin e hydrate afforded the pyrazolo[3,4-b]pyridine 7c. Treatment of 2a,c o r 2e,g with cyanoethanoic hydrazide afforded the N-(cyanoacetamido)pyr idines 9a,b. The dienes 2d,f,g afforded the pyridones 11a-c on treatme nt with acetic acid and hydrochloric acid mixture. Compounds 11b,c wer e also formed on treatment of 2b,c with acetic acid hydrochloric acid mixture. The reaction of 2d,g with ethanolic sodium ethoxide gave the ethoxypyridines 13a,b. (C) 1996 John Wiley & Sons, Inc.