反应详情

A solution of 2-methylmaleic anhydride (3) (1.8 g, 16.1 mmol) in benzene (10 mL) is added to a refluxed solution of 4 (5.5 g, 13.5 mmol) in benzene (50 mL) under nitrogen. After refluxing for 6 hrs, TLC indicated complete consumption of 12. The reaction mixture is evaporated to dryness, and the residue is chromatographied on silica gel using hexanes-acetone (4:1) to yield E-4-cinnamoylmethylidene-2-methylbut-2-en-4-olide (5) (2.35 g, 73%) as yellow needles [from chloroform-methanol (1:1)]: mp 160–161 C°, UV (MeOH), ?max (log e) 208 (4.18), 238 (3.98), 334 (4.50) nm; IR (KBr) ?max, 1770, 1678, 1627, 1588, 1451, 1375, 1209, 1098, 1039, 990, 911, 877, 754, 698, 545; 1H NMR (400 MHz, CDCl3) d 8.10 (1H, s, H-3), 7.64 (1H, d, J=16.0 Hz, H-4′), 7.59 (2H, m, H-6′,10′), 7.42 (3H, m, H-7′,8′,9′), 6.88 (1H, d, J=16.0 Hz, H-3′), 6.48 (1H, s, H-1′), 2.11 (3H, s, Me-2); 13C NMR (100 MHz, CDCl3) d 188.3 (s, C-2′), 169.2 (s, C-1), 159.2 (s, C-4), 144.0 (d, C-4′), 137.0 (d, C-3), 136.4 (s, C-2), 134.3 (s, C-5′), 131.0 (d, C-8′), 129.1 (2C, d, C-6′,10′), 128.6 (2C, d, C-7′,9′), 127.5 (d, C-3′), 106.0 (d, C-1′), 11.2 (q, Me-2) (NMR assignments were based on 2D HMBC and NOESY experiments); HRESIMS m/z [M+H]+ 241.0841 (calcd for C15H13O3, 241.0859), [M+Na]+ 263.0659 (calcd for C15H12O3Na, 263.0678), [M+K]+ 279.0400 (calcd for C15H12O3K, 279.0418).

1. temperatureAfter refluxing for 6 hrs
2. customconsumption of 12
3. customThe reaction mixture is evaporated to dryness