To 300g gallic acid in 300ml H2O was added 900ml warm 50% NaOH while bubbling alkaline pyrogallol-washed nitrogen through the solution and then 900g Me2SO4 within 1h at 40-50°C. The mixt. cooled and 75 g. NaOH added, the mixt. refluxed for 3 hrs. and cooled again, 900ml conc HCl with 1 kg crushed ice added, the ppt. sepd., washed with H2O, dissolved in 2000ml 40% EtOH, and kept 12 hrs. at 0°C pptg. 3,4,5-trimethoxybenzoic acid.
200 g 3,4,5-trimethoxybenzoic acid was refluxed with 114g SOCl2 for 2 h, excess SOCl2 distd. off at reduced pressure, the mixt. cooled, and the solidified product suspended in petroleum ether, refluxed 10 min. with 1% activated carbon, filtered, and cooled to 0°C yielding 3,4,5-trimethoxybenzoyl chloride.
To 150g 3,4,5-trimethoxybenzoyl chloride in 2100ml Et2O was added slowly with stirring 120g aniline in 510ml Et2O and the mixt. allowed to stand 1h, filtered, stirred with 2% NaCl, filtered, and washed with NaCl soln. yielding the anilide, of which (100 g) with 75 g PCl5, warmed to 70°C to evolve HCl and heated further to dist. off excess PCl5 yielded the imidochloride. To 90 g if the imidochloride in 2000ml Et2O was added an ethereal SnCl2 soln., the mixt. held at 0° for 12 hrs., the pptd. Sn salt sepd., washed with Et2O, and refluxed with AcOH-HCl-H2O (200:175:325 ml) for 1h, cooled, diluted with H2O and extd. 3 times with Et2O, dried. and crystd. to yield 3,4,5-trimethoxybenzaldehyde.
Reference: Arch. ital. sci. farmacol. [3] 2, 376-83 (1952); Chem Abs 3314h (1956)
