2-AMINO-4,6-DIFLUOROBENZOTHIAZOLE synthesis

Yield: 28%

Reaction Conditions:

Stage #1:ammonium thiocyanate with bromine;acetic acid at 10; for 0.5 h;Cooling with ice;
Stage #2:2,4-difluorophenylamine with acetic acid at 0 - 20;

Steps:

General Procedure of Method A for 2-chlorobenzothiazole Synthesis(GP2)^5,6
General procedure: GP2-1: In a flask were added by ammoniumthiocyanate (2.2 eq) and HOAc (5 volume), bromine (1.1 eq) in HOAc (5 volume)was added dropwise under ice-cooled condition, which was stirred at 10 ⁰Cfor 30 min. After filtering off the solid, the filtrate was collected.In aseparate flask, aniline (1.0 eq) and HOAc (5 volume) were added. Then thefiltrate prepared above was added dropwise under 0 ⁰C within 5 min.The mixture was kept stirring at rt overnight. After removal of solvent underreduced pressure, the residue was diluted with EA, neutralized with saturatedNa₂CO₃ solution, separated, passed through a pad ofCelite, and concentrated to dryness. The crude was purified by silica gelcolumn.GP2-2: To a round-bottomed flaskwas added 2-aminobenzothiazole (1.0eq) and CuCl₂ (1.2 eq) in acetonitrile (10 volume), followed by slowaddition of tert-butyl nitrite (1.2eq). The gas evolved immediately. The reaction was greatly exothermic, and, ifnecessary, ice-water cooling was applied. The mixture was then stirred at rtfor hours, which was monitored by TLC. After completion, the reaction wasquenched by 1M HCl, washed by 1 M HCl twice and extracted by EA. The combinedorganic layer was washed by brine, dried over Na₂SO_4, concentrated and purifiedby flash column to give the product.

References:

Lv, Fengping;Li, Zhi-Fang;Hu, Wenhao;Wu, Xiaohua [Bioorganic and Medicinal Chemistry,2015,vol. 23,# 24,p. 7661 - 7670] Location in patent:supporting information