5-(4-[1,3]Dioxolan-2-yl-2-fluorophenoxy)pyrazine-2-carboxamide → 5-(2-Fluoro-4-formylphenoxy)pyrazine-2-carboxamide

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Reaction Steps

Combine formic acid (90%, 453 mL) and crude 5-(4-[1,3]dioxolan-2-yl-2-fluorophenoxy)pyrazine-2-carboxamide (Example 737, Part D) (32.81 g, approximately 0.09 mole) and stir initially a clear yellow solution, which becomes a thick slurry in an hour at room temperature. Stir overnight at room temperature till the reaction complete by HPLC. Quench the reaction with deionized water (1 L) and extract with dichloromethane (4×4 L). Combine the extracts and mix with aqueous sodium bicarbonate solution. Concentrate on a rotary evaporator to give a slurry of a solid in water (when the separation of layers not possible). Extract the mixture with ethyl acetate (4×1 L) and concentrate the combined extracts to a yellow solid (29.65 g). Form slurries successively four times with boiling methanol (1 L) and filter while hot. Combine the filter cakes and dissolve in enough boiling methanol to give a clear solution. Concentrate the solution to approximately 1 liter and allow to crystallize at 0° C. Filter the resulting slurry at 0° C. and dry the filter cake under vacuum at room temperature to give the title compound (17.79 g, 75.7%). 1H NMR (DMSO-d6) δ 7.70 (t, 1H, ArH), 7.78 (s, 1H, HetH), 7.86-7.93 (m, 2H, ArH), 8.14 (s, 1H, HetH), 8.73 (d, 2H, amide), 10.0 (s, 1H, CHO); 13C NMR (DMSO-d6) δ 116.884, 124.606, 126.980, 133.186, 134.967, 140.765, 144.016, 152.493, 154.974, 159.276, 164.057, 190.777; MS (ES+) m/z 262.3 (M+H).

Provenance & Evidence