Hydrochloric Acid → (E)-1-(2,6,6-trimethylcyclohex-2-en-1-yl)but-2-en-1-one

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Reaction Steps

100 g of 2,6,6-trimethyl-1-[4-hydroxy-hepta-1,6-dien-4-yl]-cyclohex-2-ene have been added at room temperature and under stirring to a solution of 80 g of potassium tert-butoxide in 180 ml of dimethylformamide, while the temperature raised to 60°. After having been left at this temperature for 6 min., the mixture is put into an aqueous HCl solution [150 ml of conc. HCl/200 ml H2O]. A vapour phase distillation has given 4 l of distillate which was then extracted with petrol ether (80°-100°). After the usual treatments of separation, drying and evaporation of the organic extracts, 71 g of a mixture of iso- α-damascone and α-damascone were obtained. Analogous yields were obtained by carrying out the reaction in accordance with the above described method but by replacing aqueous HCl by diluted acetic acid. The complete isomerization of iso- α-damascone into α-damascone can be effected on the obtained mixture by means of an acidic isomerizing agent according to the process described for instance in Swiss Pat. No. 537,352.

Provenance & Evidence