Triphenylphosphine → 5,6-Dimethyl-2-nitro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine

Participants

Reaction Conditions

Reaction Steps

To a mixture of 250c (1.129 g, 5.27 mmol) and triphenylphosphine (4.14 g, 15.8 mmol) in anhydrous THF (40 mL) cooled at 0° C. was added the solution of di-isopropyl azodicarboxylate (DIAD) (3.19 g, 15.8 mmol) in THF (15 mL) over a period of 30 minutes while maintaining the internal temperature below 5° C. The reaction mixture was warmed to 30° C. and stirred at this temperature for 5 h. The mixture was then quenched with water (50 mL) and concentrated under reduced pressure. The residue was extracted with dichloromethane (3×80 mL). The combined organic layer was dried over Na2SO4 and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by silica-gel column chromatography eluting with dichloromethane/methanol (80:1 to 30:1) to afford 250d (0.83 g, 80%) as yellow solid. MS-ESI: [M+H]+ 197.2

Provenance & Evidence