Acetic Acid → Benzyl 1-tert-butyl-1,4-dihydrospiro[indazole-5,4'-piperidine]-1'-carboxylate

Participants

Reaction Steps

Benzyl 10-((dimethylamino)methylene)-9-oxo-3-azaspiro[5.5]undec-7-ene-3-carboxylate (59.2 g, 167 mmol) was dissolved in ethanol (835 mL). To the solution was added acetic acid (20 mL, 345 mmol) and tert-butylhydrazine hydrochloride (29.1 g, 234 mmol). The reaction was heated to reflux for 1 hour. The reaction was cooled to room temperature and concentrated to an orange oil. Purification by flash column chromatography (20-40% ethyl acetate/heptanes) afforded the title compound (50 g, 79%) as a pale yellow solid. +ESI (M+H) 380.5; 1H NMR (400 MHz, CDCl3, δ): 7.26-7.40 (m, 5 H), 7.17 (s, 1 H), 6.66 (d, J=9.95 Hz, 1 H), 5.77 (d, J=10.15 Hz, 1 H), 5.12 (s, 2 H), 3.38-3.64 (m, 4 H), 2.58 (s, 2 H), 1.60 (s, 12 H), 1.50 (br. s., 1 H).

Provenance & Evidence