Trifluoromethanesulfonic acid → 2,3-dihydrospiro[furo[2,3-g][1,4]-benzodioxine-8,8'-[1,3]thiazolo[5,4-e]indol]-7'(6'H)-one

Participants

Reaction Steps

To a solution of 6′-(4-methoxybenzyl)-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,8′-[1,3]thiazolo[5,4-e]indol]-7′(6′H)-one (1.9 g, 4.0 mmol) in dichloromethane (40 mL) and trifluoroacetic acid (40 mL) was added at ambient temperature trifluoromethanesulfonic acid (1.8 mL, 20 mmol). The mixture was stirred at ambient temperature for 16 h and concentrated in vacuo. Water was added to the residue and the mixture was extracted with ethyl acetate. The combined organic extracts were washed with saturated aqueous sodium bicarbonate and water, dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. The residue was purified by column chromatography and eluted with 50% ethyl acetate in hexanes to afford 2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,8′-[1,3]thiazolo[5,4-e]indol]-7′(6′H)-one (0.65 g, 44%): 1H NMR (300 MHz, CDCl3) δ10.86 (s, 1H), 9.06 (s, 1H), 7.97 (d, J=8.5 Hz, 1H), 7.14 (d, J=8.5 Hz, 1H), 6.54 (s, 1H), 6.21 (s, 1H), 4.68 (s, 2H), 4.19-4.01 (m, 4H); MS (ES+) m/z 353.1 (M+1).

Provenance & Evidence