Allyl phenyl ether → 1-(2-Ethyl-3,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-1-one

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A few crystals of diphenyl are added to a suspension, cooled to 5°-10° C and held under a nitrogen atmosphere, of 2.4 g (0.35 g-atoms) of finely cut lithium wire in 40 ml of absolute tetrahydrofuran. 2 ml of a solution of 9.4 g (70 mmol) of allyl phenyl ether in 10 ml of absolute ether are then added. After a greenish coloration sets in, the rest of the solution is added dropwise at -15° C. After completion of the addition, the mixture is stirred for 30 minutes at 0° C. The resulting allyl lithium solution is decanted off from excess lithium and transferred to a dropping funnel. This solution is added dropwise to a solution, cooled to -60° C and maintained under nitrogen, of 4.48 g (20 mmol) of 2-ethyl-3,6,6-trimethyl-2-cyclohexene-1-carboxylic acid ethyl ester in 40 ml of absolute ether. After completion of the addition, the mixture is left to warm to room temperature, poured on to ice-water and extracted with three portions of hexane. The combined hexane extracts are washed neutral with three portions of water, dried over sodium sulphate and evaporated. By fractional distillation of the residue there are obtained 3.75 g (85%) of 2-ethyl-3,6,6-trimethyl-1-[but-3-enoyl]-2-cyclohexene; boiling point 57°-58° C/0.04 mm Hg; nD20 = 1.4865.

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