1,8-Diazabicyclo(5.4.0)undec-7-ene → 3-[(1S)-1-azidoethyl]-5-bromopyridine

Participants

Reaction Steps

To a solution of (1R)-1-(5-bromopyridin-3-yl)ethanol (10 mmol) in tetrahydrofuran (40 mL), cooled to 0° C., was added diphenylphosphoryl azide (4.3 mL, 20 mmol) in one portion followed by 1,8-diazabicyclo[5.4.0]undec-7-ene (3 mL, 20 mmol) dropwise over 30 minutes. After this time the reaction mixture was allowed to warm slowly to room temperature and was stirred overnight. The mixture was diluted with ethyl acetate (50 mL) and water (50 mL), the two phases separated and the aqueous phase extracted with ethyl acetate (3×50 mL). The combined organic phases were washed with brine (50 mL), dried (MgSO4) and concentrated under reduced pressure to give a black liquid which was purified by flash chromatography (silica, ethyl acetate/hexanes) to give 3-[(1S)-1-azidoethyl]-5-bromopyridine (1.7 g, 75%) as a colourless liquid. A mixture of m-toluamide (164 mg, 1.21 mmol), 3-[(1S)-1-azidoethyl]-5-bromopyridine (227 mg, 1 mmol), copper (I) iodide (9.6 mg, 0.05 mmol), N,N-dimethylethylene diamine (0.011 mL, 0.1 mmol) and potassium carbonate (276 mg, 2 mmol) in dioxane (1 mL) was heated in a microwave reactor at 110° C. for 30 minutes then at 160° C. for a further 30 minutes. After this time the mixture was allowed to cool to room temperature, was diluted with ethyl acetate (5 mL) and was filtered through Celite. The filtrate was concentrated under reduced pressure to give a brown oil which was purified by flash chromatography (silica, ethyl acetate/dichloromethane) to give N-{5-[(1S)-1-azidoethyl]pyridin-3-yl}-3-methylbenzamide (80 mg, 28%) as a colourless oil.

Provenance & Evidence