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

Participants

Reaction Conditions

Reaction Steps

tert-Butyl 2-methylspiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (1.0 g, 3.27 mmol), potassium carbonate (497.7 mg, 3.60 mmol) and trifluoromethanesulfonate; 5-(trifluoromethyl)dibenzothiophen-5-ium (1.32 g, 3.27 mmol) were combined in acetonitrile (10 mL). The reaction mixture was heated at 60° C. for 16 h. The reaction was evaporated to dryness and the residue was dissolved in dichloromethane. The organics were washed with water and brine, dried over sodium sulfate and evaporated. The crude material was purified by silica gel chromatography eluting with 0-50% ethyl acetate in hexanes to give tert-butyl 2-methyl-6-(trifluoromethyl)spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (812 mg, 66%). ESI-MS m/z calc. 373.2, found 374.5 (M+1)+; Retention time: 1.21 minutes (3 min run). 1H NMR (400 MHz, CDCl3) δ 6.52 (d, J=3.8 Hz, 1H), 5.91 (d, J=3.8 Hz, 1H), 3.98 (t, J=6.0 Hz, 2H), 3.93-3.76 (m, 2H), 3.32 (t, J=6.0 Hz, 2H), 3.26-3.08 (m, 2H), 2.36 (s, 3H), 2.11-1.99 (m, 2H), 1.81-1.65 (m, 2H), 1.47 (s, 9H).

Provenance & Evidence