To a solution of 130 mg of 10l, 30 mg of anisole and 100 ul of methanol in 1 ml of dioxane was added 400 μl of 4N HCl in dioxane. The reaction mixture was stirred for 5 h and then quenched by addition of 10 ml of 5% aq. NaHCO3 and extracted with ethyl acetate. The organic layer was washed once with water, dried and concentrated. The residue was treated with diisopropyl ether, to afford 95 mg of 10u as white crystalline material; Mp 201-203° C.; Rf 0.20 (heptane-acetone 1/1). MS-ESI: [M+1] 499.94 and 501.95. NMR (CDCl3) 1.30 (d, 6, isoC3H7), 3.88 (s, 3, OCH3), 4.72 (m, 1, isoC3H7), 6.70, 7.18 (2×s, 2, Ar—H), 6.93, 7.13, 7.41 (3×m, 3, thiophene-H).
