Figure 2

Light-induced dimethylation of 1a with methanol leading to (rac)-rivastigmine (3aa). Typical conditions (entry 1): 1a (1.0 mmol), Cu/TiO₂ (22 mg), CH₃OH (10 mL, 250 mmol, 250 equiv), 300 W Xe lamp with a UV-cold mirror (λ = 300–470 nm), Ar (1 atm), 25 °C. Metal content in 22 mg photocatalysts: Cu/TiO₂ (5 wt% Cu, 16 µmol Cu), Au/TiO₂ (5 wt% Au, 5.1 µmol Au), Pt/TiO₂ (5 wt% Pt, 3.2 µmol Pt), Pd/TiO₂ (5 wt% Pd, 9.5 µmol Pd), and Ag/TiO₂ (4 wt% Ag, 8.5 µmol Ag) as determined by ICP-AES. Yields of 3aa were determined by GC/MS or ¹H NMR using 2,2-dimethylpropan-1-ol as an internal standard. Isolated yields are in parentheses. ^*Conditions: 1a (50 µmol), CH₃OH (5 mL), 50 °C. ^†Conditions: 1a (0.2 mmol), CH₃OH (2 mL), 32 W UV-LED lamp (λ₀ = 365 nm).