Pyrrolidine → 2'-Methyl-6',7'-dihydro-2'H-spiro[piperidine-4,5'-pyrano[3,2-c]pyrazole]-7'-one

Participants

Reaction Steps

Pyrrolidine (3.0 g, 3.5 mL, 42 mmol) was added to a solution of 1-(4-hydroxy-1-methyl-1H-pyrazol-3-yl)ethanone (5.93 g, 42.3 mmol) in methanol (50 mL). The mixture was stirred at room temperature for 2 hours before addition of N-Boc-piperidone (8.43 g, 42.3 mmol). The mixture was stirred at room temperature overnight before concentration to dryness. The crude material was purified by CombiFlash (120 g column, 30-50% EtOAc/hexanes gradient) to afford desired product containing unreacted starting material. This material was triturated with 30% EtOAc/hexanes, the solids were filtered and air dried to afford tert-butyl 2′-methyl-7′-oxo-6′,7′-dihydro-1H,2′H-spiro[piperidine-4,5′-pyrano[3,2-c]pyrazole]-1-carboxylate (6.8 g, 50%).

Provenance & Evidence