Ortho Fries rearrangement of 3-methylcatechol diacetate; 2, 3-dihydroxy-4-methylacetophenoneSyntheticPage 41 (2001)
Submitted 14th Aug 2001, published 15th Aug 2001
A contribution from the Harrowven Group, Southampton
Aluminium chloride (Lancaster).
Finely powdered 3-methylcatechol diacetate (25 g, 0.12 mol) and ground aluminium chloride (16.0 g, 0.12 mol) were mixed and heated to 90 oC for 5 minutes. The temperature was then raised to 120 oC and maintained at that temperature for 25 minutes. The resulting brown solid was allowed to cool and quenched by the addition of dilute HCl (200 mL) and extracted into dichloromethane (3 x 200 mL). The combined extracts were dried (MgSO4), filtered and the solvent removed from the filtrate in vacuo. The crude product was recrystallised from petrol to yield the acetophenone as a white solid (3.6 g, 22 mmol, 18%).
After performing this reaction 3-4 times (always on a 25 g scale) we found that careful control of temperature is critical in this reaction. The reaction mixture must be at 90 oC for no more than 5 minutes and after this time should be heated rapidly (ie over 2-3 minutes) to 120 oC or else the para product may be observed.
MP: 65-67 C (petrol). Lit. 70 C (petrol)
1H NMR (300 MHz, CDCl3) 12.50 (1H, s), 7.19 (1H, d), 6.69 (1H, d), 5.80 (1H, s), 2.61 (3H, s), 2.31 (3H, s).
Cullinane, N. M.; Edwards, B. F. R.; J. Chem. Soc., 1958, 2926.
Doppler, T.; Schmid, H.; Helv. Chim. Acta., 1979, 62, 314.
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