[Br:1][C:2]1[C:3]([C:8]([F:11])([F:10])[F:9])=[N:4][NH:5][C:6]=1[CH3:7].O.C1(C)C=CC(S(O)(=O)=O)=CC=1.[O:24]1[CH:29]=[CH:28][CH2:27][CH2:26][CH2:25]1>C(Cl)(Cl)Cl>[Br:1][C:2]1[C:3]([C:8]([F:9])([F:11])[F:10])=[N:4][N:5]([CH:25]2[CH2:26][CH2:27][CH2:28][CH2:29][O:24]2)[C:6]=1[CH3:7]To a solution of 4-bromo-5-methyl-3-trifluoromethyl-1H-pyrazole (1.4 g, 6.2 mmol, 1.0 equiv) in chloroform (31 ml) was added p-toluene sulphonic acid monohydrate (118 mg, 0.62 mmol, 0.1 equiv). The solution was cooled to 0° C. and 3,4-dihydro-2H-pyran (0.85 ml, 9.3 mmol, 1.5 equiv) was added drop-wise over 5 minutes. The mixture was allowed to warm to room temperature for 1 hour and the solvents were removed under reduced pressure. The crude mixture was purified by column chromatography (SiO2), eluting with 0→25% EtOAc-petrol over a linear gradient to afford the title compound 1.4 g (59%), LCMS (PS-A) Rt 3.72 min [M+H]+ 314.
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