Making piperonal from vanillin is not the same as making 3,4,5 TMB from vanillin one is a demethylation and the other is a methylation. Vanillin must be demethylated first to give 3,4 dihydroxybenzaldehyde before piperoanl can be made from it.
What thet hell does 4-Hydroxy-3-methoxybenzaldehyde(C8H8O3)be used interchangebly with 3,4,5-trimethoxybenzaldehyde (C10H12O4)? mean?
If you explain what your trying to do maybe someone coudl help you.