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[摘要]：The cyclization of 5-cyano-6-cyanoimino-3,4-dihydropyridin-2(1h)-ones with amines, leading to pyrido[2,3-d]pyrimidines, is studied. Four play all important role oil the direction of cyclization: (1) the planarity of the reaction area; (2) the cyclization proceeds by the nucleophilic attack of all amidine onto ail electrophilic group which call be either a cyano group or all alkylamidine; (3) the basicity of the amine plays all important role, the ionization Of the Substrate making more difficult the formation of the aforementioned amidine which is needed for the cyclization; and (4) the nucleophilic attack and the tautomerization of the cyclization product are processes which call occur practically Simultaneously, so that the electronic movement involved in the tautomerization process coincides with the one which happens In the nucleophilic attack, both processes promoting each other. |
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