Yield: 72%

Reaction Conditions:

Stage #1:3-fluoro-6-methylaniline with hydrogenchloride;sodium nitrite in water at 0; for 1 h;
Stage #2: with tin(ll) chloride in water at 20; for 2 h;

Steps:

337.1 Step 1. (5-Fluoro-2-methylphenyl)hydrazine hydrochloride
Step 1.
(5-Fluoro-2-methylphenyl)hydrazine hydrochloride
To a solution of 2-methyl-5-fluoroaniline (1.31 g, 10.5 mmol) in concentrated HCl_(aq) (12 mL) was added a solution of sodium nitrite (1.08 g, 15.7 mmol) in water (4.0 mL) slowly at 0° C.
After the reaction mixture was stirred at 0° C. for 1 h, a solution of tin(II) chloride (5.97 g, 31.5 mmol) in concentrated HCl_(aq) (6.0 mL) was added.
The solution was stirred for another 2 h at room temperature.
The solids were collected by filtration and washed with cold water and n-hexane to give (5-fluoro-2-methylphenyl)hydrazine hydrochloride (1.34 g, 72%) as a yellow solid. ¹H NMR (DMSO-d₆, 400 MHz) δ 10.26 (br s, 2H), 8.06 (br s, 1H), 7.11 (dd, 1H), 6.75 (dd, 1H), 6.66 (ddd, 1H), 2.11 (s, 3H).

References:

National Health Research Institutes;Ueng, Shau-Hua;Yeh, Shiu-Hwa;Lin, Shu-Yu;Shih, Chuan US2017/253569, 2017, A1 Location in patent:Paragraph 0915-0916