Triphenyl phosphite → (S)-methyl 6-oxo-6,6a,7,8-tetrahydro-5H-azeto[1,2-a]pyrido[3,2-e]pyrazine-3-carboxylate

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(S)-methyl 6-(2-(methoxycarbonyl)azetidin-1-yl)-5-nitronicotinate (0.90 g, 3.05 mmol) was dissolved in dichloromethane (Volume: 15.24 ml) and to this solution was added triphenyl phosphite (9.46 mg, 0.030 mmol), ammonium metavanadate (0.021 g, 0.183 mmol) and Pt/C (5% wt.) (0.119 g, 0.030 mmol). The reaction mixture was hydrogenated at 100 psi at 25° C. for 2 h. LCMS showed complete conversion of the starting material to the corresponding amine, but no cyclization product was observed. The reaction mixture was filtered through a short plug of celite and the plug and precipitate were washed well with dichloromethane (30 mL) and methanol (20 mL). The combined filtrates were concentrated in vacuo (LC: CR1) and dissolved in AcOH (5 mL) (LC: AA-rt). This solution was heated to 80° C. for 5 min (LCMS—AA-90C-5 min—complete conversion to the desired product) and concentrated in vacuo. The residue was crystallized with ethyl ether (20 mL) and sonicated until a fine suspension was obtained The precipitate was filtered off and dried in vacuum to afford (S)-methyl 6-oxo-6,6a,7,8-tetrahydro-5H-azeto[1,2-a]pyrido[3,2-e]pyrazine-3-carboxylate (0.5840, 2.504 mmol, 82% yield) as a light pink solid. [M+H] calc'd for C11H11N3O3, 234; found, 234.

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