1. Viallon, L., Reinaud, O., Capdevielle, P., Maumy, M.; Synthesis1995, in press.
2. Synthesis of New Bicyclic Quinones: 2H-1-Benzopyran-5,8-quinones and Related Compounds
3. Viallon, L., Reinaud, O., Capdevielle, P., Maumy, M.; Tetrahedron1995, in press.
4. To a stiffed solution of pure quinone 2a (mp = 196°C) (1.0 g, 3 mmol) in MeOH (30 ml) and 1M aqueous KHCO3 (15 ml), MMPP (2.5 g, 4.2 mmol) was added within 2 h. After 24 h at room temperature, MeOH was distilled under vacuum and the organic layer extracted with ether (100 ml) and dried over MgSO4. The crude product was purified by column chromatography on silica gel with a mixture of cyclohexane and ethyl acetate (40/60) as an eluent to yield pyranone 3a (0.791 g, 2.46 mmol, 82%).
5. 3a, colorless crystals, mp = 138°C, Analysis. Found %: C, 74.62; H, 5.98; N, 4.39; Calc.% for C20H19NO3: C, 74.75; H, 5.96; N, 4.36; 1H NMR (CDCl3 / TMS) δ: 2.65 (s, 3H, N-Me); 3.55 (s, 3H, -OMe); 5.25 (s, 1H, 0=C-CH=C-N); 6.65 (s, 1H, N-CH-); 7.05 (s, 1H, O-CH=C-OMe); 7.1 – 7.5 (m, 10 H, 2 Ph). IR (KBr), v (cm−1 ):1702, 1668, 1632.