Water → 4-[5-(5,5-Dimethyl-[1,3]dioxan-2-yl)-2-(4-fluoro-phenyl)-2H-pyrazol-3-yl]-pyridine

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Reaction Steps

A solution of 4-[5-dimethoxymethyl-2-(4-fluoro-phenyl)-2H-pyrazol-3-yl]-pyridine (3 g, Reference Example 1), 2,2-dimethylpropane-1,3-diol (2.2 g) and p-toluene sulfonic acid (2 g) in dry toluene (50 ml) was refluxed for 1 hour with azeotropic removal of water. The reaction mixture was cooled to room temperature then evaporated. The residue was partitioned between ethyl acetate (50 ml) and saturated aqueous sodium carbonate solution (50 ml). The organic phase was washed three times with water (50 ml), then dried over magnesium sulphate and then evaporated. The residual oil was triturated twice with diethyl ether then recrystallised from diethyl ether to give the title compound as white needles (1 g), m.p. 150-151° C. [Elemental analysis: C,67.69; H,5.98; N,12.09%. Calculated for C20H20FN3O2: C,67.97; H,5.70; N,11.89%]. MS: 354 [MH]+. RF=0.42 (ethyl acetate, determined by thin layer chromatography on silica).

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