https://www.thevespiary.org/rhodium/Rhodium/chemistry/bromodimethoxybenzaldehyde.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/bromodimethoxybenzaldehyde.html)
.Subsequent fractions gave 1.5g (5%) of 6-bromo-2,5-dimethoxybenzaldehyde (3), mp 102-103°C (EtOH).
SWIM's previous post gave the wrong sequencing on the ring, but the idea still works...
1. 6-bromo-2,5-dimethoxybenzaldehyde
2. methoxide ion in DMF(or EtOAc) with CuI will give the 2,5,6-trimethoxybenzaldehyde (or 2,3,6-tmb; however you want to call it)
As for the bromination of 2,5-DMB, I don't see any easy way to end up with TMA-6 from there.
Seems better(easier) than what you proposed, even if you only get a 2% yield. Sorry if SWIM didn't like your proposed synthesis, it was just too much work. If there was a way to increase the yield in the bromination step, selectivity at the 6 (or 1; however you want to call it) position, then this would great. No formylations, and relatively OTC - if you make the 2,5-DMB and corresponding alkoxides by yourself, which can be done OTC.