Example 11
A solution of acetal (300 g, 1.16 mol) in acetone (3.0 L) was heated to reflux and 4N HCl (250 mL) was added over 1.0 h to the refluxing solution. TLC analysis indicated complete consumption of the starting material. The reaction mixture was concentrated under reduced pressure and phases were separated. The organic phase was diluted with ethyl acetate (1.5 L) and washed with saturated NaHCO3 solution (1.0 L), water (1.0 L) and brine (1.0 L), and then dried over anhydrous Na2SO4. All of the aqueous phases were combined and extracted with ethyl acetate. The extracts were combined and dried over anhydrous Na2SO4. The organic solutions were filtered and concentrated under reduced pressure. The crude product was triturated with petroleum ether and diethyl ether (5:1) and the resulting solid was collected by vacuum filtration and washed with petroleum ether and ethyl acetate (10:1). The filtrate was concentrated and chromatographed using 0-15% ethyl acetate/petroleum ether to give another crop of desired product. All white to light yellow solids were combined and weighed 40 g (43% yield). 1H NMR (500 MHz, CDCl3) δ 10.08-10.06 (m, 1H), 8.53-8.50 (m, 1H), 4.49 (q, J=7.1 Hz, 2H), 1.44 (t, J=7.1 Hz, 3H). MS ESI m/z calcd for C7H8NO3S [M+H]+ 186.01; found 186.01.
