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38. Cyclizations of 5,6-difunctionalized pyrido[2,3-d]pyrimidinetriones
Stadlbauer W., Dang V. T.,
Third International Electronic Conference on Synthetic Organic Chemistry (ECSOC-3), www.mdpi.org/ecsoc/, September 1-30, 1999; Poster A0001.

Abstract: Pyrido[2,3-d]pyrimidine-2,4,7-triones 1 with reactive substituents in the 5- and 6-position were used as synthons for new polyheterocyclic systems. 5-azido-6-phenyl derivatives 1 (X= N3, Y = Ph) cyclize thermally to indoles 2, 5-azido-6-nitro compounds 1 (X= N3, Y = NO2) react to furoxanes 3, from 5-azido-6-acyl compounds 1 (X=N3, Y=COR) ring closed isoxazoles 4 are obtained. Thermally induced cyclization to tetracyclic quinolines 5 is achieved with 5-phenylamino-6-formyl compounds 1 (X= NHPh, Y=CH=O). Reaction of 5-hydroxy-6-amino derivatives 1 (X= OH, Y= NH2) with acyl halides gives oxazoles 6. 5-Hydroxy compounds 1 (X=OH, Y= H) react with malonates to give pyranes 7.
Determination of the suitable reaction conditions were investigated by DSC (differential Scanning Calorimetry). Some of these compounds revealed interesting bioliogical activity.

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