Trifluoroacetic acid → 3-{4-[(2-Aminoethyl)amino]-1,2,5-oxadiazol-3-yl}-4-(3-chloro-4-fluorophenyl)-1,2,4-oxadiazol-5(4H)-one hydrochloride

A premixed solution of triisopropylsilane (3.4 mL, 17 mmol) and trifluoroacetic acid (44 mL, 570 mmol) was added to 4-(3-chloro-4-fluorophenyl)-3-(4-{[2-(tritylamino)ethyl]amino}-1,2,5-oxadiazol-3-yl)-1,2,4-oxadiazol-5(4H)-one (6.5 g, 11 mmol) and the resulting suspension was stirred at 25° C. for 30 min. The reaction mixture was filtered and washed with trifluoroacetic acid. The filtrate was concentrated to an oil which was diluted with methanol (25 mL), cooled to 0° C., treated with 4 M HCl in 1,4-dioxane (14 mL), and stirred at 25° C. for 15 min. The mixture was concentrated to a solid that was treated with diethyl ether (50 mL) and filtered. The solid was washed with diethyl ether (50 mL) and dried to give the desired product (4.1 g, 98%) as a white solid. LCMS for C12H11ClFN6O3 (M+H)+: m/z=341.1. 1H NMR (300 MHz, DMSO-d6): δ 8.05-8.00 (m, 4 H), 7.75-7.69 (m, 1 H), 7.64 (dd, J=9.1, 8.8 Hz, 1 H), 6.77 (dd, J=5.9, 5.9 Hz, 1 H), 3.54-3.47 (m, 2 H), 3.04-2.99 (m, 2 H).