video tutorial Can thiourea be used to demethylate vanillin

Vanillin demethylation using Fioria — summary

• Reagents: AlCl3 (20 g) prepared in situ from zinc chloride and aluminum powder, vanillin (20 g, dried), Fioria (11.4 g).
• AlCl3 preparation: heat ZnCl2 and Al powder to form a white, fluffy AlCl3; collect and dry to protect from air.
• Vanillin solution: dissolve vanillin in dried dichloromethane (DCM), starting with ~40 mL and adjusting as needed; avoid premature crystallization by maintaining solvent volume.
• Reaction setup: dry glassware, 500 mL two‑neck flask, pressure‑equalized addition funnel, condenser, and dry calcium chloride tube; maintain cold cooling water for DCM; perform dropwise addition with stirring under gentle reflux.
• Reaction sequence: combine AlCl3 and Fioria in DCM, then slowly add vanillin solution over ~1.5 hours; observe color changes from pale yellow to yellow goo and then orange/red; stir and reflux gently, scraping lumps as needed to maintain mixing; total addition time ~1.5 h, then continue stirring/reflux for 2 hours, then overnight (8 h) with heating off.
• Hydrolysis and workup: cool and add dilute hydrochloric acid (15 mL of 36% HCl with 40 mL water) to hydrolyze complexes; separate layers; extract aqueous phase with ethyl acetate (30 mL×3); dry organic with MgSO4 and concentrate to yield a red oily liquid; target product is 2.5 g (about 10% or less).
• Purification and yield issues: extensive solvent trials failed to crystallize the product; sodium bisulfite adduct formed a brown crystalline material (4–5 g) but remained impure; overall yield is poor compared to a previous pyridine run; ongoing investigations and requests for theories.