DEHYDROGENATION OF 5,6-DIHYDROPYRIDO[2,3-d]PYRIMIDIN-7(8H)-ONES: A CONVENIENT LAST STEP FOR A SYNTHESIS OF PYRIDO[2,3-d]PYRIMIDIN-7(8H)-ONES

Two new protocols for the dehydrogenation of 5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones to pyrido[2,3-d]pyrimidin-7(8H)-ones are described. The first one uses NaH in DMSO an affords the corresponding pyridopyrimidines when an aryl substituent is present at C6. The second one is of a more general use, allowing dehydrogenation of aryl and alkyl substituted 5,6-dihydropyridopyrimdines upon treatment with Na2SeO3 in DMSO.