To a solution of piperonal (1, 3.00 g, 19.9 mmol) in CH2Cl2 (100 mL) was added (carbethoxyethylidene)triphenylphosphorane (2,14.5 g, 40.0 mmol), and the reaction mixture was stirred for 24 h at room temperature. The mixture was then concentrated at reduced pressure, and the residue was purified by flash column chromatography on silica gel (hexanes/EtOAc,10:1) to afford olefin 3 (4.45 g, 95%) as a colorless oil: 1H NMR (400 MHz, CDCl3) d 7.58 (s, 1H), 6.92 (d, J = 1.7 Hz, 1H), 6.90 (dd, J = 7.9, 1.7 Hz, 1H), 6.82 (d, J = 8.0 Hz, 1H), 5.97 (s, 2H), 4.24 (q, J = 7.1 Hz, 2H), 2.10 (d, J = 1.6 Hz, 3H),1.33 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 168.7,147.6, 138.3, 129.9, 126.9, 124.6, 109.5, 108.2, 101.2, 60.7, 14.3,1 4.0; IR (ATR, cm-1): 2981, 2902,1698, 1628, 1502, 1489,1442, 1258, 1224; HRMS (EI) m/z calcd for C13H14O4 (M+) 234.0892, found 234.0895.
Fig The synthetic step of PMK ethyl glycidate
