3,5-Dichloro-1-fluoropyridinium triflate → 2-Cyano-7-fluoro-6-hydroxybenzothiazole
Reaction equation
[C:1]([C:3]1[S:4][C:5]2[CH:11]=[C:10]([OH:12])[CH:9]=[CH:8][C:6]=2[N:7]=1)#[N:2].[O-]S(C(F)(F)[F:18])(=O)=O.ClC1C=[N+](F)C=C(Cl)C=1>ClCCl>[C:1]([C:3]1[S:4][C:5]2[C:11]([F:18])=[C:10]([OH:12])[CH:9]=[CH:8][C:6]=2[N:7]=1)#[N:2]Participants
4
Reactant 2
Product 1
Reagents, catalysts & solvents 1
Procedure
To a suspension of 2-cyano-6-hydroxybenzothiazole (2.0 g, 11.4 mmol) in dichloromethane (50 ml) in a 250-ml round-bottomed flask was added 3,5-dichloro-1-fluoropyridinium triflate (6.1 g, 19.3 mmol). The reaction flask was fitted with a reflux condenser and the mixture was brought to reflux under argon atmosphere for 53 hr. Additional 3,5-dichloro-1-fluoropydidinium toiflate was added (1.0 g, 3.2 mmol) and reaction continued for another 22 hr. Additional 3,5-dichloro-1-fluoropylidinium triflate was added (1.0 g, 3.2 mmol)and reaction continued for another 27 hr. Additional 3,5-dichloro-1-fluoropyridinium triflate was again added (1.0 g, 3.2 mmol) and reaction continued for another 72 hr. The reaction mixture was concentrated by rotoevaporation to give a brown residue that was purified by flash chromatography with 100 g of silica gel and methylene chloride as eluting solvent. The title compound was obtained as a white solid. Yield: 0.97 g (44%).