Boron trifluoride etherate → 2-Methoxy-2,6,6-trimethyl-9-methylidenebicyclo[3.3.1]nonane

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Reaction Steps

120 g (0.563 mol) of dihydro-α-ionone, 65 g (0.612 mol) of trimethyl orthoformate and 200 ml of methylene chloride are treated dropwise while stirring during 15 minutes with a solution of 8 g of boron trifluoride etherate in 60 ml of methylene chloride and the mixture is subsequently held under reflux for 105 minutes. The reaction mixture is cooled and poured into 500 ml of a 5% aqueous potassium hydroxide solution. After the addition of 500 ml of methylene chloride and vigorous intermixing the phases are separated, the organic phase is washed with water and the solvent is distilled off. The residue (197.1 g) is fractionated in a vacuum over a 15 cm Widmer column. There are obtained 100.2 g of product of b.p. 44°-47° /0.06-0.07 mbar (yield 87% of theory based on pure dihydro-α-ionone) as a colorless liquid which contains 72.3% of exo isomer and 20.1% of endo isomer of the desired bicyclo-nonane.

Provenance & Evidence