p-Toluenesulfonic acid monohydrate → (S)-2-Chloro-5-(2,2-dimethyl-1,3-dioxolan-4-yl)-3-fluoropyridine

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Reaction Conditions

Reaction Steps

A suspension of 113 (5.39 g, 28.2 mmol) in 2,2-dimethoxypropane (58 mL, Sigma-Aldrich) was cooled with an ice bath. Para-toluene sulfonic acid monohydrate (PTSA, 0.54 g, 2.82 mmol, Sigma-Aldrich) was added to form a reaction mixture. The ice bath was removed and the reaction mixture was stirred at a temperature of about 25° C. for 16 hrs. Thereafter, the mixture was cooled with an ice bath, treated with saturated aqueous sodium bicarbonate, and extracted with EtOAc. The organic layer was separated, washed with brine, dried (Na2SO4), and concentrated to provide 5.65 g of 114 as an oil (87% yield). 1H NMR (CDCl3) δ: 1.48 (3H, s), 1.54 (3H, s), 3.71 (1H, m), 4.37 (1H, m), 5.11 (1H, t, J=6.76 Hz), 7.53 (1H, dd, J=1.93, 8.63 Hz), 8.18 (1H, d, J=1.88 Hz). LC/MS (M+1): m/z=232.

Provenance & Evidence