[CH3:1][N:2]1[C:6](=[O:7])[CH2:5][CH:4]([C:8]([NH:10][CH2:11][C:12]2[C:17]([CH3:18])=[N:16][CH:15]=[CH:14][N:13]=2)=O)[CH2:3]1.N.C(OCC)(=O)C.CO>CS(O)(=O)=O.O=P12OP3(OP(OP(O3)(O1)=O)(=O)O2)=O.CO>[CH3:1][N:2]1[CH2:3][CH:4]([C:8]2[N:13]3[CH:14]=[CH:15][N:16]=[C:17]([CH3:18])[C:12]3=[CH:11][N:10]=2)[CH2:5][C:6]1=[O:7]1-Methyl-N-((3-methylpyrazin-2-yl)methyl)-5-oxopyrrolidine-3-carboxamide (330 mg, 1.329 mmol) was dissolved in Eaton's reagent (2 ml) and the reaction mixture was stirred at 60° C. for 18 hour. Then the reaction mixture was poured into an ice-bath and basified with 7N ammonia in methanol (20 ml). The resulting mixture was extrated with chloroform/iso-propanol (9/1) five times. The combined organic extracts were dried (Na2SO4) and concentrated in vacuo. The residue (280 mg) was stripped with toluene twice and with dichloromethane twice. An additional crop (53 mg) was obtained by extraction of the water layer with chloroform/iso-propanol (9/1) twice and drying and concentrating as described before. In total 333 mg of crude 1-methyl-4-(8-methylimidazo[1,5-a]pyrazin-3-yl)pyrrolidin-2-one was obtained which was used in the next reaction without further purification.
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