hydrogenchloride; potassium hydroxide; p-toluenesulfonic acid monohydrate; isopentyl nitrite in ice-water; ethanol

1: 3',4'-difluoroaniline With hydrogenchloride; sodium nitrite in water T=0°C; 0.666667 h; 2: With sodium acetate in water 0.5 h; 3: 2-methyl-3-oxobutanoic acid ethyl ester With potassium acetate more than 3 stages;