Benzene → 2,7,9,9-Tetramethyl-1,4-dioxaspiro[4,5]dec-6-en-8-one

Participants

Reaction Steps

To a 2-liter flask fitted with a reflux condenser, a water separator, and a stirrer is charged 265 g of 2,6,6-trimethylcyclohex-2-en-1,4-dione (prepared by the method described in Helv. Chim. Acta 39, 2041 [1956]), 2669 g of propylene glycol, 500 ml of benzene, and 1 g of p-toluene-sulfonic acid. The reactants are stirred and refluxed until no additional water is collected in the water separator. The product is washed with water to a pH of 6, and the solvent is stripped off. The residue is vacuum distilled through a 9" Goodloe column to yield 257 g of product, boiling point 92° at 1 mm Hg (80% yield).

Provenance & Evidence