Hydrochloric Acid → 4-(Tert-butyl)-2-((tert-butylamino)methyl)-6-(5-methylpyridin-2-yl)phenol dihydrochloride

Participants

Reaction Steps

A mixture of paraformaldehyde (661 mg, 22.0 mmol) and tert-butylamine (2.32 mL, 22.0 mmol) in isopropanol (10 mL) was gently refluxed under nitrogen for 1 hour. A solution of 4-(tert-butyl)-2-(5-methylpyridin-2-yl)phenol (1.062 g, 4.4 mmol) in isopropanol (5 mL) was added and the reaction mixture refluxed for 6 days. The cooled reaction mixture was then concentrated under reduced pressure and the residue partitioned between ethyl acetate (80 mL) and 1.0 M aqueous sodium hydroxide solution (80 mL). The organic phase was separated, washed with water (80 mL) and saturated brine (80 mL), dried (MgSO4), filtered and concentrated under reduced pressure to give a yellow syrup. The crude 3,4-dihydro-2H-benzo[e][1,3]oxazine was dissolved in absolute ethanol (90 mL), 1.0 M aqueous hydrochloric acid solution (30 mL) added and the reaction mixture stirred at room temperature for 9 days. The reaction mixture was concentrated under reduced pressure to remove ethanol, the resulting aqueous solution diluted to 50 mL with 1.0 M aqueous hydrochloric acid solution and washed with ethyl acetate (50 mL). The aqueous phase was basified to pH 7-8 by the addition of solid sodium carbonate and the resulting milky suspension extracted with ethyl acetate (80 mL). The organic phase was separated, washed with half saturated brine (80 mL), dried (MgSO4), filtered and concentrated under reduced pressure to give a yellow syrup. The product was dissolved in absolute ethanol (50 mL), hydrogen chloride-ethanol solution (1.25 M, 18.44 mL, 23.05 mmol) added, the mixture stood for 20 minutes then concentrated under reduced pressure to give a cream solid. Diethyl ether (50 mL) and absolute ethanol (15 mL) were added and the resulting suspension stirred vigorously overnight then filtered to give 4-(tert-butyl)-2-((tert-butylamino)methyl)-6-(5-methylpyridin-2-yl)phenol dihydrochloride (1.466 g, 83% yield) as a hygroscopic white solid.

Provenance & Evidence