6-Amino-3-methylpyrido pyrazine

Condensation of 3-amino-2-(methylamino)pyridine 647 with diethyl 2-oxomalonate in boiling ethanol afforded 2-carbethoxy-4-methylpyrido[2,3- ]pyrazin-3(4//)-one 213 <1996JHC1737>. On the other hand, condensation of 647 with diethyl oxaloacetate gave ethyl [2(l//)-oxopyrido[2,3- ]pyrazine-3(4//)-ylidene]carboxylate 648 in addition to the formation of pyridodiazepine 649 as a by-product <1996JHC1737>. However, the condensation of 647 with diethyl 2-oxoadipate gave the 2-ethoxycarbonylpropyl analogue 650 (Scheme 30) <1994FA259>. 

Cyclocondensation of 3-amino-2-methylaminopyridine 647 or 2-amino-3-methylaminopyridine 651 with 2-keto-glutaric acid gave 2-carboxyethyi-4-methylpyrido[2,3-i)]pyrazin-3(4/7)-one 652 and its 3-carboxyethyl-2(l/7)-one isomer 653, respectively (Equation 54) <1994FA259>. 

Partially hydrogenated pyrazine moieties in pyrido[2,3-6]pyrazines are aromatized by permanganate11,67 or iodine.7 Thus, ethyl 8-amino-3,4-dihydro-2-methylpyrido[2,3-6]pyrazine-6-carba-mate (1) with potassium permanganate in acetone yields 84% of the fully aromatic compound 2,11 another example being the oxidation of l,2,3,4-tetrahydro-2,3-dimethylpyrido[2,3-A]pyrazine (3)-67 nh2 nh2... 

Ethyl 8-Amino-2-methylpyrido[2,3-6 pyrazine-6-carbamate (2) Typical Procedure 11... 

Ethyl 8-amino-3,4-dihydro-2-methylpyrido[2,3-6]pyrazine-6-carbamate (1 1.09 g, 4.37 mmol) was dissolved in warm acetone (250 mL), and the solution was allowed to cool to rt. A 0.27% solution of KMn04 in acetone was added slowly with stirring over a period of 1 h until the color of permanganate persisted (ca. 2.08 mmol was consumed). The Mn02 which formed was removed by filtration and the filtrate was evaporated to dryness in vacuo yield 0.910 g (84%) mp >260°C (EtOH). 

Diazotization of the amino substituent of 6-amino-4-methylpyrido[2,3-/ >]pyrazin-3(4/7)-one in aqueous solution is followed by decomposition of the diazonium cation to give 4-methy]pyri-do[2,3-h]pyrazine-3,6(4//,5//)-dione.18... 

By treatment with aqueous hydrobromic acid, l-[(3-amino-4-pyridyl)amino]propan-2-ol is cyclized to give l,2,3,4-tetrahydro-3-methylpyrido[3,4-/>]pyrazine.111... 

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See also in sourсe #XX -- [ ]

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