US Patent 5041616
Preparation of Aryl Ketones
Example 1:
A mixture of p-toluic acid (22.2g, 0.163mol), p-xylene (100ml), and trifluromethanesulfonic acid (5ml, 0.056mol) was heated at reflux for 21 hours in a 300ml flask equipped with a Dean-Stark trap, after which time 3ml of water had been collected in the trap. The progress was measured with GC as well as by the amount of water collected. After 6 hours, 22% of the starting material had been converted to 2,5,4’-trimethylbenzophenone. The mixture was extracted with water, with 5% sodium hydroxide and again with water. Evaporation of the organic layer gave 24g (0.11mol) of 2,5,4’-trimethylbenzophenone, 66% of theory.
Example1; modified:
The procedure in Example 1 was repeated without a Dean-Stark trap. After 4 hours of reflux, only about 6% of the starting material had been converted to product. The amount of product was not increased significantly after refluxing an additional 6 hours.
Example 2:
Benzoic acid (20g, 0.16mol), p-xylene (100ml), and trifluoromethanesulfonic acid (5ml) were heated at reflux in a 300ml flask equipped with a Dean-Stark trap. After 16 hours, the mixture was extracted with 100ml of 6% sodium hydroxide, washed with 100ml of water, dried over Mg sulfate and evaporated to give 15.4g (0.073mol) of 2,5-dimethylbenzophenone. The aqueous sodium hydroxide extract was acidified to give 8.1g (0.066mol) of unreacted benzoic acid.
Example 3:
Hydroquinone (11.0 g, 0.1 mole), octanoic acid (30.2 g, 0.21 mole), heptane (110 mL), and methanesulfonic acid (10 mL, 0.14 mole) were heated at reflux (98.degree. C.) for 5 hours in a 300 mL flask equipped with a Dean-Stark trap. During this time, 3 mL of water was collected. The sulfonic acid layer was separated, and the heptane layer was washed once with 50 mL of water and twice with 50 mL portions of saturated, aqueous sodium bicarbonate solution. The mixture was filtered to remove 5 g of product, octanoylhydroquinone octanoate ester, while evaporation of the organic layer gave 17.3 g. The total yield of octanoylhydroquinone was 22.3 g, 94% of theory.