Trifluoroacetic acid → 8-(4-methoxybenzyl)-2-methyl-5,8-dihydro-4H-pyrazolo[3,4-c]thiazolo[5,4-f]isoquinoline

Participants

Reaction Conditions

Reaction Steps

To a mixture of (Z)-6-((dimethylamino)methylene)-2-methyl-5,6-dihydrobenzo[d]thiazol-7(4H)-one (3.5 g, 16.9 mmol) and 1-(4-methoxybenzyl)-1H-pyrazol-5-amine (3.5 g, 17.2 mmol) was added trifluoroacetic acid (2.3 mL, 29.2 mmol). The reaction mixture was heated at 100° C. for 2 hours. The reaction mixture was then poured into ice-cooled water (100 mL) and extracted with dichloromethane (3×75 mL). The combined organic extracts were dried using sodium sulfate and concentrated under reduced pressure to give a dark residue. The crude product was purified by flash column chromatography (SiO2, gradient from 100% chloroform to 2% methanol in chloroform) to a residue, which was further purified by crystallization from methanol and isopropanol to give the pure desired product (0.8 g, 19%) as a solid. 1H NMR (CDCl3, 400 MHz): δ 7.86 (s, 1H), 7.76 (s, 1H), 7.36 (d, J=8.0 Hz, 2H), 6.82 (d, J=8.0 Hz, 2H), 5.59 (s, 2H), 3.75 (s, 3H), 3.17 (t, J=6.8 Hz, 2H), 3.09 (t, J=6.8 Hz, 2H), 2.77 (s, 3H); LCMS [M+H]: 363.

Provenance & Evidence