1: With ammonium chloride; sodium t-butanolate in tert-butyl alcohol T=20 - 100°C; 0.5 h; 2: With hydrogenchloride in trans-1,3-dioxane; dichloromethane T=0 - 20°C; 1 h; 3: With sodium hydroxide; malonic acid di(tert-butyl)-ester; citric acid more than 3 stages;

hydrogenchloride in ethyl acetate