Hydrochloric Acid → Ammonium Hydroxide

Participants

Reaction Steps

(S)-5-Amino-1,3-dihydrospiro[indene-2,3′-pyrrolo[2,3-b]pyridin]-2′(1′H)-one (6.10 g, 24.3 mmol, described in Intermediate 3) and p-chloranil (5.97 g, 24.3 mmol) were suspended in a mixture of 1-BuOH (6 mL) and conc. hydrochloric acid (6 mL, 73 mmol) and the mixture was heated to reflux. Crotonaldehyde (2.04 g, 29.1 mmol) in 1-BuOH (4 mL) was added dropwise over 20 min. After a further 20 min at reflux, the mixture was allowed to cool to ambient temperature and 10 N NaOH (7.3 mL, 73 mmol) was added and the neutralized mixture was concentrated in vacuo to give a brown residue. The crude product was purified by silica gel chromatography, eluting with a gradient of CH2Cl2:MeOH:NH4OH—100:0:0 to 95:4.5:0.5, to give the title compound. MS: m/z=302 (M+1).

Provenance & Evidence