2,4-Dimethoxy-5-thiophen-2-yl-benzaldehyde from Ex-6A (7.81 g), 4-acetylbenzoic acid (4.9 g), MeOH (60 mL) and DMF (150 mL) were sequentially charged into a clean reaction vessel fitted with a stir bar and nitrogen inlet adapter. After complete dissolution LiOMe (4.60 g) was added and the resulting solution was aged for 5 h. The reaction was diluted with H2O (200 mL) and transferred to a separatory funnel containing iPrOAc (100 mL). The layers were cut and the aqueous layer was acidified to a pH of 1 with 3 N HCl. The resulting precipitate was filtered and then dried on the filter funnel under a stream of N2. The crude product was then dissolved in THF (60 mL) and crystallized with the addition of heptane (60 mL). The product was filtered and then dried to a constant weight in the vacuum oven affording 8.9 g (75% yield) of the title compound as a yellow solid, m.p. 213–216° C. 1H-NMR (300 MHz, CDCl3): 8.20 (d, 2H, J=8.5 Hz), 8.09 (d, 1H, J=16.1 Hz), 8.06 (d, 2H, J=8.5 Hz), 7.85 (s, 1H), 7.52 (d, 1H, J=16.1 Hz), 7.40 (m, 1H), 7.30 (dd, 1H, J=5.2 and 1.7 Hz), 7.08 (dd, 1H, J=5.2 and 3.6 Hz), 6.53 (s, 1H), 3.98 (s, 3H), 3.97 (s, 3H); EIMS m/z=394 (M+). Anal. calc. for C22H18O5S: C, 66.99; H, 4.60; S, 8.13; found: C, 66.71; H, 4.59; S, 8.10.
