[CH3:1][C:2]1([CH3:14])[C:10]2[CH:9]=[N:8][C:7](N)=[N:6][C:5]=2[C:4]([CH3:13])([CH3:12])[O:3]1.N([O-])=O.[Na+].[Cl:19]CCl>Cl.[Cl-].[Zn+2].[Cl-]>[Cl:19][C:7]1[N:8]=[CH:9][C:10]2[C:2]([CH3:14])([CH3:1])[O:3][C:4]([CH3:13])([CH3:12])[C:5]=2[N:6]=1To a solution of 5,5,7,7-tetramethyl-5,7-dihydro-furo[3,4-d]pyrimidin-2-ylamine (38.6 g, 200.0 mmol, 1.0 equiv) in dichloromethane (80 mL) and 37% HCl (70 mL) at 0° C. was added zinc(II) chloride (46.3 g, 340.0 mmol, 1.7 equiv) in portions within 30 min. After the addition was completed, sodium nitrite (23.5 g, 340.0 mmol, 1.7 equiv) was added slowly within 3 h keeping the reaction temperature below 5° C. After stirring for an additional time period of 1 h, the reaction mixture was poured on ice and then extracted with dichloromethane (3×200 mL), the combined organic phases washed with a sat. solution of sodium carbonate (2×100 mL), dried over MgSO4 and concentrated by evaporation under reduced pressure. The reaction product was dissolved in diethyl ether (200 mL), filtered and the organic solvent removed by evaporation under reduced pressure yielding 33.2 g (78%) of the title compound. MS (EI): 213 [M]+.
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