Synthesis of Gallacetophenone (2,3,4-trihydroxyacetophenone)
Procedure
In a 250mL RB flask, fitted with a reflux condenser to which is attached a calcium chloride tube, 28g (0.21 mole) of freshly fused and finely powdered zinc chloride (Note 1) is dissolved in 38mL of glacial acetic acid by heating in an oil bath at 135–140°C. Forty grams (0.37 mole) of 95% acetic anhydride is then added to the clear, pale brown liquid, followed by the addition in one lot of 50g (0.4 mole) of distilled pyrogallol (Note 2). The mixture is heated at 140–145°C (Note 3) for 45 minutes with frequent and vigorous shaking. The unused acetic anhydride and acetic acid are removed by distilling under reduced pressure. The red-brown cake is broken up by the addition of 300mL of water with mechanical stirring for a few minutes. The mixture is cooled in ice water, filtered with suction, and washed with cold water. The crude material, 45–50g, is crystallized from 500mL of boiling water saturated with sulfur dioxide. The yield of straw-colored needles melting at 171–172°C is 36–38g (54–57% of the theoretical amount). On saturating the mother liquor with salt and cooling to 10°C, 4–5g of crude material is obtained, which on recrystallization yields 3–4g of pure material (Note 4).
Notes
1.) A good quality of zinc chloride must be used, and it is an advantage to fuse it immediately before use.
2.) Variations in the proportions of acetic acid, acetic anhydride, and zinc chloride did not result in increased yields.
3.) The temperature must be carefully regulated and must not exceed 150°C. In this preparation, as well as in the preparation of other ketones by the Nencki reaction, higher temperatures lead to the formation of a highly colored and resinous product which probably contains a little diketone.
4.) This method has been used for the preparation of other phenolic ketones such as resacetophenone, 2-acetyl-1-naphthol, 2-phenylacetyl-1-naphthol, and 2-phenylpropionyl-1-naphthol.
Reference: Organic Syntheses, CV 2, 304 (http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?rxntypeid=2&prep=CV2P0304)
(http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?rxntypeid=2&prep=CV2P0304)
Methylenedioxybenzene Derivates. 27.
The Synthesis of Dimethoxy-Methylenedioxy-Allylbenzenes
Franz Dallacker
Chem. Ber. 102, 2663-2676 (1969) (https://www.thevespiary.org/rhodium/Rhodium/pdf/apioles.dallacker.pdf)
(https://www.thevespiary.org/rhodium/Rhodium/pdf/apioles.dallacker.pdf)
Abstract
The synthesis of 2,3-Dimethoxy-4,5-Methylenedioxy- (Dillapiole), 2,5-Dimethoxy-3,4-Methylenedioxy- (Parsley Apiole), 4,6-Dimethoxy-2,3-Methylenedioxy-, 2,6-Dimethoxy-3,4-Methylenedioxy-, 5,6-Dimethoxy-2,3-Methylenedioxy- and 4,5-Dimethoxy-2,3-Methylenedioxy-allylbenzene is described. (In German)