HETEROCYCLES STRUCTURALLY INFLUENCED BY A SIDE CHAIN .7. 3-PHENACYLIDENE-3,4-DIHYDRO-1H-PYRIDO[2,3-B]PYRAZIN-2-ONES AND 2-PHENACYLIDENE-1,2-DIHYDRO-4H-PYRIDO[2,3-B]PYRAZIN-3-ONES

摘要

Condensation of 2,3-diaminopyridine (1) with ethyl o-, m- and p-substituted benzoylpyruvates 2-9 gave two isomeric products. The preferential formation of one or the other isomer has been achieved by different reaction conditions. All the products appear to exist in the enamine form as evidenced by their H-1 nmr and ir spectra. [References: 6]