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General Procedure for C-Acetylation of Baylis-Hillman Adducts
To a stirred solution of 6 mmol Sm powder (0.9 g) and
6 mmol Ac2O (0.6 g) in 15 mL THF, 5 mol% FeCl3, 4 mol% I2 and 1 mmol Baylis-Hillman adduct 1 were added. The resulting mixture was then allowed to reflux in the air. Until completion of the reaction, 3 mL HCl (1 M) was then added to quench the reaction and the mixture was successively exacted with CH2Cl2 (3 × 20 mL). The organic phase was washed with 15 mL sat. brine, dried over anhyd Na2SO4, and filtered. The solvent was removed under reduced pressure to give the crude products, which were purified by column chromatography using EtOAc and PE (1:10) as eluent. Selected spectroscopic data for compounds 2 follow.
Compound 2a (R = Ph): 1H NMR (500 MHz, CDCl3): δ = 7.93 (s, 1 H), 7.37-7.27 (m, 5 H), 3.80 (s, 3 H), 3.62 (s, 2 H), 2.25 (s, 3 H). 13C NMR (500 MHz, CDCl3): δ = 206.1, 167.8, 142.2, 135.0, 128.9, 128.7, 128.6, 126.6, 52.2, 42.5, 30.1. IR (film): 3058, 2952, 2847, 1703, 1639, 1575, 1492, 1437, 1359, 1264, 1098, 764, 700 cm-1.
Compound 2b (R = 3-MeOC6H4): 1H NMR (500 MHz, CDCl3): δ = 7.90 (s, 1 H), 7.30-6.84 (m, 4 H), 3.81 (s, 3 H), 3.80 (s, 3 H), 3.63 (s, 2 H), 2.26 (s, 3 H). 13C NMR (500 MHz, CDCl3): δ = 206.6, 168.4, 160.1, 142.8, 136.9, 130.2, 127.4, 121.6, 115.2, 114.5, 55.8, 52.8, 43.2, 30.7. IR (film): 3001, 2953, 2850, 1706, 1637, 1600, 1580, 1488, 1433, 1359, 1247, 1098, 790, 690 cm-1.