Reaction Steps
10% Cd/Pb couple (192 mg, 1.55 mmol) was added to a rapidly stirring mixture of 45 (107 mg, 77.3 μmol), THF (2.5 mL) and 1N NH4OAc (2.5 mL). The reaction mixture was allowed to stir for 3 hours at which point TLC (95:5 v/v CHCl3/MeOH) showed the formation of desired PBD accompanied by side-products. The solids were collected by filtration and rinsed with H2O and DCM. The aqueous layer was extracted with DCM (3×10 mL) and the organic extracts were combined, washed with brine (50 mL) and dried (MgSO4). Filtration and evaporation of solvent afforded the crude product which was purified by flash column chromatography (gradient elution: CHCl3 to 99:1 v/v CHCl3/MeOH) to afford the imine 46 as a yellow glass (32.5 mg, 55%): 1H NMR (400 MHz, CDCl3) δ 7.89 (d, 2H, J=3.9 Hz), 7.53 (s, 2H), 7.39 (s, 2H), 7.34 (d, 4H, J=8.8 Hz), 6.90 (d, 4H, J=8.8 Hz), 6.82 (s, 2H), 4.43-4.38 (m, 2H), 4.18-4.05 (m, 4H), 3.95 (s, 6H), 3.83 (s, 6H), 3.58 (ddd, 2H, J=16.2, 11.5, 1.9 Hz), 3.38 (ddd, 2H, J=16.3, 5.1, 1.6 Hz), 2.01-1.94 (m, 4H), 1.73-1.66 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 162.6, 161.3, 159.2, 151.3, 148.1, 140.3, 126.2, 126.0 (×2), 123.2, 122.0, 119.1, 114.3, 111.9, 110.9, 68.8, 56.2, 55.4, 53.9, 35.6, 28.7, 22.6.
