Formic Acid → Trismethoxyresveratrol

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To a round-bottomed flask (100 mL) equipped with magnetic stir bar was charged anhydrous DMF (6 mL) and triethylamine (960 mg, 9.5 mmol, 5 equiv). In dropwise fashion, 98% formic acid (437 mg, 9.5 mmol, 5 equiv) was added over 10 min. After allowing the mixture to cool to room temperature, a previously prepared solution of 7 (790 mg, 2 mmol) in anhydrous DMF (3 mL) was added in one portion followed by Pd(OAc)2 (21 mg, 0.09 mmol) and DPPF (105 mg, 0.18 mmol). A reflux condenser was equipped and the reaction mixture was heated under N2 to an internal temperature of 80° C. After 20 min the mixture had become dark and the reaction was complete by TLC analysis. The mixture was cooled to room temperature and partitioned between H2O (50 mL) and Et2O (50 mL). A rag layer formed and the mixture was filtered through medium filter paper. The organic layer was separated and washed with H2O (50 mL) and then brine (50 mL). After drying over anhydrous MgSO4, evaporation of the organic phase under reduced pressure left a pale brown oil that slowly crystallized (470 mg, 91%), mp. 55-57° C., lit 56-57° C. 1H NMR (CDCl3): δ 7.45 (d, J=8.9 Hz, 2H), 7.05 (d, J=16 Hz, 1H), 6.90 (d, J=16 Hz, 1H), 6.89 (d, J=8.6 Hz, 2H), 6.65 (d, J=2.2 Hz, 2H), 6.38 (t, J=2.5 Hz, 1H), 3.83 (s, 9H); 13C NMR (CDCl3): 161.20, 139.93, 130.16, 128.96, 128.02, 126.81, 114.37, 104.57, 99.86, 55.57, 55.53. Anal. Calcd for C17H18O3: C, 75.53; H, 6.71. Found: C, 75.53; H, 6.62. (E. Späth and K. Kromp, Ber., 74, 189 (1941)).

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