A practical protocol was developed for the synthesis of 2-arylamino substituted 4-amino-5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones from α,β-unsaturated esters, malononitrile, and an aryl substituted guanidine via the corresponding 3-aryl-3,4,5,6- tetrahydropyrido[2,3-d]pyrimidin-7(8H)-ones. Such compounds are formed upon treatment of 2-methoxy-6-oxo-1,4,5,6-tetrahydropyridine-3-carbonitriles with an aryl substituted guanidine in 1,4-dioxane and are converted to the desired 4-aminopyridopyrimidines with NaOMe/MeOH through a Dimroth rearrangement. The overall yields of this three-step protocol are, generally speaking, higher than the multicomponent reaction, previously developed by our group, between an α,β-unsaturated ester, malononitrile, and an aryl substituted guanidine.

Wheland intermediates are usually unstable compounds and only a few have been isolated at very low temperatures. During our work on tyrosine kinase inhibitors, we study the bromination of 7...

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 (I) are presented. -(PEREZ-PI, I.; BERZOSA, X.; GALVE, I.; TEIXIDO, J.; BORRELL*, J. I.; Heterocycles 82 (2010) 1, 581-591, http://dx.doi.org/10.3987/com-10-s(e)28 ; Grup Eng. Mol., Inst. Quim. Sarria, Univ. Ramon Llull, E-08017 Barcelona, Spain; Eng.) -H. Toeppel 19-153

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