Hydrogen Peroxide → tert-Butyl 2'-methyl-6'-(trifluoromethyl)-3',4'-dihydro-2'H-spiro[piperidine-4,1'-pyrrolo[1,2-a]pyrazine]-1-carboxylate

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Reaction Steps

To tert-butyl 2-methylspiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (10.0 g, 32.7 mmol) in DMSO (164 mL) was added ferrous sulfate heptahydrate (9.8 mL of 1.0 M, 9.8 mmol) followed by CF3I (6.41 g, 32.7 mmol) by slow bubbling through the solution and taking the weight difference of the canister. The mixture was cooled with a ice-water bath before H2O2 (3.71 mL of 30% w/v, 32.7 mmol) dropwise over 15 min keeping the internal temperature<20° C. The mixture was poured onto 300 mL of ice water and was extracted with EtOAc (2×400 mL). The combined organic phases were washed with brine, dried over MgSO4, filtered and concentrated in vacuo. The crude material was purified column chromatography eluting with 0-10% methanol in dichloromethane with 2% iPr2NEt to give tert-butyl 2-methyl-6-(trifluoromethyl)spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (7.8 g, 64%).

Provenance & Evidence