Synt of 2,4,6-trimethoxybenzaldehyde

[hest]

For some reason this synt always disappear for mee, so ill post it here

Add 20mL POCl3 dropvise to 34g 1,3,5-trimethoxybenzene disolved in 100mL DMF at 0°C(icebath) let the reacton stir 1½houer (or to the next day dosen't matter) and pour it out in ice/wather (1L), let it stir until xtals formation is over (takes from short to loong time) filter off the xtals. Iff the xtal is pink (they sometimes are) and  you want them white disolve the aldehyde in DCM and wash the pink outh with wather (usual 4-6 washes)
edit Yeald usual >90% iff POCl3 is pure (destilate before use) but alwayes >80%

[Rhodium]

Is that one more high-yielding than the one in Pihkal, or is it only desirable because it uses cheap DMF rather than N-methylformanilide?

Here is the procedure from

Pihkal #162 (TMA-6)

(http://www.erowid.org/library/books_online/pihkal/pihkal162.shtml):

A mixture of 62.9 g N-methylformanilide and 71.3 g of POCl₃ was allowed to stand for 0.5 h producing a light claret color. There was then added 30.9 g of 1,3,5- trimethoxybenzene and the mixture heated on the steam bath for 2 h. The reaction mixture then was poured into chipped ice, and allowed to stir for several h. The dark gummy mess was extracted with 2x100 mL Et₂O (this was discarded) and then with 4x200 mL CH₂Cl₂. The latter extracts were pooled, and stripped of solvent under vacuum yielding 14 g of an amber solid. This was recrystallized from 80 mL boiling MeOH (with decolorizing charcoal employed and filtration of the boiling solution through paper) to give 10.0 g of 2,4,6-trimethoxybenzaldehyde as a white crystalline solid with a mp of 115-116°C. The literature values are generally one-degree ranges, and they are reported as high as 121°C.

[hest]

Yeald is in the 90's

[GC_MS]

I've always used DMF instead of N-methylformanilide for formylations. I've seldomly complained  

[hest]

But in the formylation of 2,5-dimethoxytoluene N-methylformanilide gives a much higer yeald, at leas in my 'lab'
:-)

[hest]

I gave some old POCl3 a shot

42,8g TMB is disolved in 300mL DMF, cooled in a icebath, and then 25mL 10years ol POCl3 is added over 60min. The reacton is left for 2H, poured out in 1,6L wather, and the nex day the TMBA is filtered off.
Yeald 43,8g(88%) og nice pink aldehyde.