Dimethylformamide → Tert-butyl 6-cyano-2-methyl-spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4'-piperidine]-1'-carboxylate

Participants

Reaction Conditions

Reaction Steps

A solution of chlorosulfonyl isocyanate (590.9 mg, 363.4 μL, 4.175 mmol) in tetrahydrofuran (2 mL) was slowly added to a solution of tert-butyl 2-methylspiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (1020 mg, 3.340 mmol) in tetrahydrofuran (9 mL) held at −78° C. (bath temperature) under an atmosphere of argon. The reaction mixture was allowed to stir for 1 hour at −78° C. N,N-dimethylformamide (732.4 mg, 775.8 μL, 10.02 mmol) was then slowly added to the cold reaction mixture. The reaction mixture was then allowed to slowly warm to room temperature. After stirring for 3 hours at room temperature the crude material was diluted with 25 mL of tetrahydrofuran, washed with a 1M solution of sodium hydroxide, followed by three washes of a saturated aqueous solution of sodium chloride. The organic layer was dried over sodium sulfate, filtered, and evaporated to dryness to yield the crude product. The crude material was purified on 80 g of silica gel utilizing a gradient of 0-70% ethyl acetate in hexanes to yield tert-butyl 6-cyano-2-methyl-spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (280 mg, 25%) as a white solid. ESI-MS m/z calc. 330.2, found 331.1 (M+1)+; Retention time: 0.94 minutes. 1H NMR (400 MHz, CDCl3) δ 6.76 (d, J=4.0 Hz, 1H), 5.97 (d, J=4.0 Hz, 1H), 4.01 (t, J=6.0 Hz, 2H), 3.98-3.76 (m, 2H), 3.36 (t, J=6.0 Hz, 2H), 3.30-3.08 (m, 2H), 2.36 (s, 3H), 2.09-1.98 (m, 2H), 1.84-1.66 (m, 2H), 1.47 (s, 9H).

Provenance & Evidence