p-Toluenesulfonic acid → beta-Damascenone

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Reaction Steps

In a 100 ml. three-necked flask fitted with a mechanical stirrer and a Dean-Stark water separator provided with a reflux condenser, a solution of 5 g. of 2,6,6-trimethyl-1-(3-acetoxy-but-1-ynyl)cyclohexa-1,3-diene in 70 ml. of methylene chloride is refluxed while stirring. Then 0.2 g. of p-toluenesulfonic acid is added and the reaction mixture is refluxed for an additional 4 to 5 hours. The reaction mixture is cooled and poured into 70 ml. of water. The organic layer is separated, subsequently washed with 10% sodium bicarbonate solution and water, and finally dried over sodium sulfate. Concentration yields 5 g. of a residue which gives on distillation 2.5 g. or 60% yield of 1-crotonoyl-2,6,6-trimethylcyclohexa-1,3-diene, b.p. 75°-80° C./0.1 mm., nD20 1.5150.

Provenance & Evidence