[CH:1]([C:3]1[CH:13]=[CH:12][C:6]([C:7]([O:9][CH2:10][CH3:11])=[O:8])=[C:5]([CH3:14])[CH:4]=1)=O.[C:15](=O)([O-])[O-].[K+].[K+]>O1CCOCC1.[Br-].C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1>[CH3:14][C:5]1[CH:4]=[C:3]([CH:1]=[CH2:15])[CH:13]=[CH:12][C:6]=1[C:7]([O:9][CH2:10][CH3:11])=[O:8]To a stirred solution of ethyl 4-formyl-2-methylbenzoate (2.8 g, 4 mmol) in 1,4-dioxane (20 mL) were added potassium carbonate (K2CO3; 3.01 g, 21.87 mmol) and methyltriphenyl phosphonium bromide (7.8 g, 21.87 mmol) at 25° C. Then the reaction mixture was heated at 100° C. for 18 h. After the reaction was deemed complete by TLC, the reaction mixture was cooled to 25° C. and filtered, and the filtrate was concentrated under reduced pressure. The crude compound was purified by flash chromatography (SiO2, 100-200 mesh; eluting with 25-30% EtOAc in n-Hexane) to afford the title compound as a solid (2.0 g, 72%): 1H NMR (400 MHz, CDCl3) δ 7.86 (m, 1H), 7.27 (m, 2H), 6.68 (dd, J=17.6, 10.8 Hz, 1H), 5.84 (d, J=17.6 Hz, 1H), 5.39 (d, J=10.8 Hz, 1H), 4.39 (m, 2H), 2.60 (s, 3H), 1.40 (m, 3H); ESIMS m/z 191.10 ([M−H]−); IR (thin film) 2980, 1716, 1257 cm−1.
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