p-Toluenesulfonic acid → 7,7a-Dihydro-2,4,6,6-tetramethyl-1,3-benzodioxol-5(6H)-one

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Reaction Steps

Preparation of the C9 unit 170 g (1.0 mol) of crystalline 3,4-dihydroxy-2,6,6-trimethyl-2-cyclohexen-1-one were suspended in 500 ml of methylene chloride. First 500 mg (2.9 mmol) of p-toluenesulfonic acid were added to the suspension and then 144 g (2.0 mol) of vinyl ethyl ether were run in at room temperature (RT) over the course of 2 hours (h). The mixture was then stirred at RT for 4 h and subsequently 100 ml of 5% strength sodium hydroxide solution were run in. The lower organic phase was separated off, and the aqueous phase was extracted once with 100 ml of methylene chloride. The combined organic phases were washed with 200 ml of water and concentrated in a rotary evaporator. The residue was dried under greatly reduced pressure (oil pump) to give 2,4,6,6-tetramethyl-7,7a-dihydro-6H-benzo[1,3]dioxol-5-one as a yellow oil which was pure by thin-layer chromatography (TLC) and almost pure by gas chromatography (GC).

Provenance & Evidence