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To a solution of acrylate (12) (1.87 g, 8.05 mmol) in CH2Cl2 (700 mL) was added second generation Grubbs' catalyst (4 mol %, 170 mg, 0.322 mmol). The reaction mixture was refluxed for 5 hours, and the solvent then was removed under reduced pressure. Column chromatography on silica gel (30% EtOAc in hexanes as the eluent) yielded the furanone (13) (1.62 g, 98%) as a brown oil, Rf=0.15 (30% EtOAc in hexanes), [α]25D −81.3° (c 1.09, MeOH); 1H-NMR (500 MHz, CDCl3) δ: 3.66 (dd, 1H, J=5.0, 5.5 Hz), 3.71 (dd, 1H, J=5.0, 5.2 Hz), 4.57 (s, 2H), 5.17 (m, 1H), 6.16 (dd, 1H, J=1.9, 3.8 Hz), 7.29-7.37 (m, 5H), 7.48 (dd, 1H, J=1.4, 4.3 Hz); 13C-NMR (125.8 MHz, CDCl3) δ: a 69.86, 74.18, 82.61, 123.03, 128.42, 128.95, 137.69, 154.32, 173.19.

1. temperatureThe reaction mixture was refluxed for 5 hours
2. customthe solvent then was removed under reduced pressure