2,6-Dihydro-4H-pyrrolo[3,4-c]pyrazole-5-carboxylic acid tert-butyl ester

157327-42-9

1280210-79-8

The reaction of tert-butyl 3-((dimethylamino)methylene)-4-oxopyrrolidine-1-carboxylate (1 g, 4.16 mmol, 1.00 eq.) with hydrazine hydrate (340 mg, 6.79 mmol, 1.63 eq.) in ethanol (10 mL) was stirred for 5 hours at room temperature. Upon completion of the reaction, the mixture was concentrated under vacuum and the resulting residue was purified by silica gel column chromatography with ethyl acetate/petroleum ether as eluent (gradient elution from 1:5 to 1:2). The final product was 250 mg of tert-butyl 4,6-dihydropyrrolo[3,4-c]pyrazole-5(2H)-carboxylate in 29% yield as a yellow solid. The product was analyzed by LC/MS (Method C, ESI): retention time RT = 1.30 min, mass spectrum m/z ~ 210.0 [M + H]+.