General procedure for the synthesis of 3-butyn-1-amine hydrochloride from N-Boc-butyn-4-amine:
1. N-Boc-butyn-4-amine (1.81 g, 0.1 mmol) was dissolved in dichloromethane (5 mL) and 5N aqueous hydrochloric acid solution (5 mL) was added. The reaction mixture was stirred vigorously at room temperature overnight. Upon completion of the reaction, the mixture was concentrated in vacuum to a minimum volume and then freeze-dried to afford 3-butyn-1-amine hydrochloride as a white solid (809 mg, 79% yield).
Steps for the synthesis of N-tert-butyl-3-alkynyl-2,2-dimethylpropionamide:
1. Triethylamine (3 mL) was added to a suspension of 3-butyn-1-amine hydrochloride (200 mg, 2.1 mmol) in dichloromethane (10 mL) and stirred for 10 min at room temperature and under nitrogen protection. Pivaloyl chloride (284.9 μL, 2.31 mmol) was then added and stirring was continued overnight at room temperature and under nitrogen protection. After completion of the reaction, the reaction mixture was concentrated in vacuum and the residue was dissolved in methanol, filtered through a SCX-2 column and eluted with methanol to afford N-tert-butyl-3-ynyl-2,2-dimethylpropionamide (265 mg, 65% yield).
