反应详情

To N-methylmaleimide (0.5 g, 4.5 mmol) in methanol (10 mL) was added bromine (232 μL, 4.5 mmol) dropwise in methanol (5 mL). The reaction mixture was stirred at room temperature for 12 hours. The solvent was removed in vacuo and dissolved in tetrahydrofuran (20 mL). Triethylamine (815 μL, 5.9 mmol) in tetrahydrofuran (5 mL) was added over 5 minutes, whereupon a precipitate formed. The reaction mixture was stirred for 24 hours. The solid was filtered off and washed with tetrahydrofuran (50 mL). Purification by flash chromatography (10% ethyl acetate in petroleum ether) afforded the desired compound as a pale yellow powder (563 mg, 2.96 mmol) in 66% yield. δH (500 MHz, CDCl3) 6.90 (s, 1H, H-3), 3.09 (s, 3H, H3-6); δC (125 MHz, CDCl3) 168.6 (C═O), 165.4 (C═O), 131.9 (C3), 131.4 (C2), 24.7 (C6); IR (solid, cm−1) 3106 (s), 1708 (s); MS (CI+) m/z, (relative intensity): 192 ([81M+H], 99), 190([79M+H], 100); Exact mass calcd for [C5H4O2N79Br]+H requires 189.9504 Found 189.9505 (CI+); m.p: 77-79° C.; UV (Acetonitrile) ε209=17100, ε238=13200, ε299=290 cm−1M−1 d3.

1. customThe solvent was removed in vacuo
2. dissolutiondissolved in tetrahydrofuran (20 mL)
3. customformed
4. stirringThe reaction mixture was stirred for 24 hours
5. filtrationThe solid was filtered off
6. washwashed with tetrahydrofuran (50 mL)
7. customPurification by flash chromatography (10% ethyl acetate in petroleum ether)