Reaction #4981

Reaction equation

2,4-dihydroxy-3-methylbenzaldehyde

Phosphoric acid

→

solid

Yield 72.0%

2,4-dimethylresorcinol

Yield 72.0%

Solvents

isopropanol

Conditions

Workup

1. 1
   Temperaturecooled in a 5 L 3-neck flask
2. 2
   Otherfitted with a magnetic stirrer
3. 3
   Otherthe solution was sparged with nitrogen
4. 4
   Other(c. 1.5 hour)
5. 5
   Otherwas again sparged with nitrogen
6. 6
   Filtrationfiltered through Celite®
7. 7
   Washthe resulting solution washed with water (4×100 mL)
8. 8
   ExtractionThe water washes were back-extracted with ethyl acetate
9. 9
   Dryingthe combined organic layers dried over sodium sulfate

Procedure

A solution of 2,4-dihydroxy-3-methylbenzaldehyde (30.0 g, 197 mmol) with isopropanol (3 L) was ice-cooled in a 5 L 3-neck flask fitted with a magnetic stirrer. Phosphoric acid (4 mL) and d10% palladium on carbon were added and the solution was sparged with nitrogen, then hydrogen. When uptake was judged to be complete (c. 1.5 hour) the solution was again sparged with nitrogen and then filtered through Celite®. The solvent was stripped off, the residue taken up in ethyl acetate, and the resulting solution washed with water (4×100 mL). The water washes were back-extracted with ethyl acetate and the combined organic layers dried over sodium sulfate and stripped down. Sublimation (95°, 0.05 torr) afforded a colorless solid (19.6 g, 72%). M.p. 107°-8° C. (Lit. 108°-109° C. [W. Baker et al., J. Chem. Soc., 2834-5 (1949).]). NMR (DMSO-d6): δ 1.969 (s, 3H), 2.037 (s, 3H), 6.220 (d, J=8.1 hz, 1H), 6.637 (d, J=8.1 hz, 1H), 7.929 (s, 1H), and 8.785 (s, 1H).

Source