A solution of 2A (1.46 g, 4.0 mmol) was dissolved in 1,2-dichloroethane (20 mL) and after addition of trimethyltin hydroxide (2.17 g, 12.0 mmol), the mixture was heated at 80° C. until TLC analysis indicated a complete reaction. After completion of the reaction, the mixture was concentrated in vacuo, and the residue was taken up in EtOAc (80 mL). The organic layer was washed with aqueous HCl (5%) (3×50 mL). The organic layer was then washed with brine and dried over Na2SO4. After removal of the solvent in vacuo, the residue was purified by flash column chromatography (SiO2, step-wise gradient from 2-20% MeOH in CH2Cl2) to give 3A (0.98 g, 70%) as a white solid. 1H NMR (600 MHz, CDCl3): δ 7.11 (2H, d, J=8.4 Hz), 6.86 (2H, d, J=8.4 Hz), 4.94 (1H, d, J=7.2 Hz), 4.53-4.60 (1H, m), 4.13 (2H, t, J=5.4 Hz), 3.58 (2H, t, J=5.4 Hz), 3.14 (1H, dd, J=13.8, 5.4 Hz), 3.04 (1H, dd, J=13.8, 5.4 Hz), 1.43 (9H, s); 13C NMR (150 MHz, CDCl3): δ 157.3, 155.5, 130.5, 128.8, 114.7, 80.2, 66.9, 54.7, 50.1, 37.0, 28.3; MS (ESI, m/z): 373 (M+Na)+.
