Synthesis of 3,4,5-Trimethoxybenzaldehyde from Gallic Acid and other AlkoxybenzaldehydesHisashi Ishii, et. al.Chem. Pharm. Bull. 31, 3024-3038 (1983)
(
https://www.thevespiary.org/rhodium/Rhodium/chemistry/trimethoxybenzaldehydes.html)
Several benzaldehyde derivatives were prepared for use as synthetic starting materials:
1. 3,5-Dimethoxybenzaldehyde was prepared by methylation of 3,5-dihydroxybenzoic acid with dimethyl sulfate in acetone in the
presence of potassium carbonate followed by reduction with LiAlH4 and by oxidation with Collins reagent in 80.3% overall yield.
2. 3,4,5-Trimethoxybenzaldehyde was also prepared by methylation of gallic acid with the same reagent
followed by reduction with Vitride and by oxidation with pyridinium dichromate (PDC) in 80.7% overall yield.
3. 2-Methoxy-4,5-methylenedioxy-benzaldehyde and 2,4,5-trimethoxy-benzaldehyde were obtained
by Vilsmeier–Haack reaction of O-methylsesamol and 1,2,4-trimethoxybenzene, respectively.
4. 5-Methoxy-2,3-methylenedioxy- and 2,3,5-trimethoxy-benzaldehyde were derived from 5-methoxy-2,3-methylenedioxy-
and 2,3,5-trimethoxybromobenzene by treatment with ethyl lithium followed by formylation with N,N-dimethylformamide (DMF).