[Cl:1][C:2]1[N:7]=[CH:6][C:5]2[CH:8]=[N:9][NH:10][C:4]=2[CH:3]=1.[F:11][C:12]([F:17])([F:16])S([O-])=O.[Na+].C(OO)(C)(C)C.[O-]S([O-])(=S)=O.[Na+].[Na+]>C(Cl)Cl.O>[Cl:1][C:2]1[N:7]=[CH:6][C:5]2[C:8]([C:12]([F:17])([F:16])[F:11])=[N:9][NH:10][C:4]=2[CH:3]=1Ref: PCT Int. Appl., 2010086251, 2010. To a suspension of 6-chloro-1H-pyrazolo[4,3-c]pyridine (1a, 1 g, 6.51 mmol), sodium trifluoromethanesulfinate (3.05 g, 19.54 mmol) in 10 mL of DCM and 4 mL of H2O, 70% tert-butyl hydroperoxide (4.19 g, 32.6 mmol) aqueous solution was added. The heterogeneous reaction mixture was stirred vigorously at r.t. After 28 hr, LCMS analysis showed partial conversion. Additional sodium trifluoromethanesulfinate (3.05 g, 19.54 mmol) and tert-butyl hydroperoxide (4.19 g, 32.6 mmol) was added and the reaction mixture was stirred over the weekend. Water, DCM and aqueous Na2S2O3 was added. A yellow solid was filtered off and the filtrate was extracted with DCM. The organic layer was concentrated and purified (50 g silica gel, eluting with 1:30 MeOH/DCM) to give 6-chloro-3-(trifluoromethyl)-1H-pyrazolo[4,3-c]pyridine as a yellow solid, which was further purified by recrystallization from MeOH/DCM/Hexane (200 mg, 13%). MS ESI calc'd. for C7H3ClF3N3[M+1]+ 222, found 222.
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