3-Fluoropentane-2,4-dione → 6-fluoro-5,7-dimethyl-1H,3H-2,4,7a,8-tetraaza-cyclopenta[a]indene-2-carboxylic acid tert-butyl ester

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Reaction Steps

A solution of 3-amino-2,6-dihydro-4H-pyrrolo[3,4-c]pyrazole-5-carboxylic acid tert-butyl ester (4.3 g; 19.2 mmol; 1 eq.) and 3-fluoropentane-2,4-dione (2.49 g; 21.1 mmol; 1.1 eq.) in AcOH (40 mL) was stirred at room temperature for 18 hours. 3-fluoropentane-2,4-dione (0.45 g; 3.83 mmol; 0.2 eq.) was added and the reaction mixture was stirred for one hour then concentrated in vacuo. The residue was partitioned between EA and 1M NaOH and the aqueous layer extracted with EA. The combined organic phase was dried over magnesium sulfate and concentrated in vacuo. Purification by column chromatography (10 to 40% EA in cyclohexane) afforded the title compound (3 g, 58%) as a white solid. HPLC (max plot) 99.4%; Rt 3.83 min. UPLC/MS: (MS+) 307.2 ([M+H]+).

Provenance & Evidence