Scheme 18.

Synthetic scheme for generating omeprazole (82a). Reagents and Conditions: Route A: (i) 1 M NaOH (2 eq.), EtOH, RT, 8 h; (ii) catalyst: V₂O₅, NaVO₃, NH₄VO₃, [(CH₃COCH₂COCH₃)₂VO] (0.0001–0.1 eq.), H₂O₂: 10%–70% aqueous or organic solution (1–3 eq.), solvent: halogenated hydrocarbons, ethers, alcohols, ketones, nitriles, or H₂O, temperature: 0 °C to boiling point of the solvent, 0.5–24 h, 89%–93%. Route B: (iii) condensation, conditions not specified in patent; (iv) [(CH₃COCH₂COCH₃)₂VO] (0.006 eq.), 30% H₂O₂, acetone, 0–5 °C for 1 h then 20–22 °C for 1 h, 90%; (v) 10% NaOH, nitrogen atmosphere, 50 °C, 3 h; (vi) CO₂, extraction into 1:1 v/v isopropanol/toluene, reflux, 20–30 min, 42% (across steps (v) and (vi)).