Hexachloroethane → 3,3-Difluoro-4-[8-(2,3,4-trifluoro-phenyl)-[1,2,4]triazolo[1,5-a]pyridin-2-ylamino]-piperidine-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

To a suspension of 8-(2,3,4-trifluorophenyl)-[1,2,4]triazolo[1,5-a]pyridin-2-amine (prepared in analogy to example 66a-c, 200 mg, 757 μmol) and hexachloroethane (215 mg, 908 mmol) under argon in dry THF (10 mL) was added triethylamine (230 mg, 317 μL, 2.27 mmol) followed by trimethylphosphine (1 M in THF, 908 μl, 908 μmol). The reaction mixture was stirred at room temperature for 0.5 hous, then tert-butyl 3,3-difluoro-4,4-dihydroxypiperidine-1-carboxylate (see example 247e, 230 mg, 908 μmol) was added and the mixture was heated to 150° C. in the microwave for 30 minutes. A solution of decaborane (92.5 mg, 98.4 μL, 757 μmol) in MeOH (1 mL) was added to the reaction mixture, then stirred at room temperature for 12 hours. Again a solution of decaborane (92.5 mg, 98.4 μL, 757 μmol) in MeOH (5 mL) was added and heated to 70° C. for 18 hours. Aqueous NaHCO3 solution was added to the reaction mixture, the aqueous phase was extracted with CH2Cl2, the organic layers were combined, dried over Na2SO4, filtered and the solvents evaporated. The residue was purified by flash chromatography (silica gel, 50 g, 0% to 15% MeOH/NH4OH (9:1) in dichloromethane), whereby 85 mg of intermediate imine, 3,3-difluoro-4-[(E)-8-(2,3,4-trifluoro-phenyl)-[1,2,4]triazolo[1,5-a]pyridin-2-ylimino]-piperidine-1-carboxylic acid tert-butyl ester, was isolated, which was again dissolved in dry MeOH (3 mL). Decaborane (21.6 mg, 23.0 μL, 177 μmol) was added and heated to 70° C. for 30 minutes. Aqueous NaHCO3 solution was added to the reaction mixture, the aqueous phase was extracted with CH2Cl2, the organic layers were combined, dried over Na2SO4, filtered and the solvents evaporated. The residue was purified (together with impure product fractions from first chromatography) by flash chromatography (silica gel, 50 g, 0% to 15% MeOH/NH4OH (9:1) in dichloromethane) to yield title compound as white foam (300 mg, 82%). MS ISP (m/e): 484.3/428.1/384.2 (13/100/41) [(M+H)+/(M−tBu)+/(M−Boc)+].

Provenance & Evidence