Trifluoroacetic acid → (3aRS,7aSR)-2-benzyl-7,7-dimethoxy-2,3,3a, 4,7,7a-hexahydro-1H-4-isoindolone

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Reaction Steps

To a solution of 22.9 g of 4,4-dimethoxy-2,5-cyclohexadien-1-one [J. Org. Chem., 52, 2763 (1987)] and 46 cm3 of N-butoxymethyl-N-trimethylsilylmethylbenzylamine in 150 cm3 of dry dichloromethane are added dropwise 3 cm3 of trifluoroacetic acid. Once the reaction mixture has reached reflux it is allowed to return to room temperature and is then stirred for for one hour. After addition of 5 g of potassium carbonate, the suspension obtained is filtered and the filtrate is concentrated to dryness under reduced pressure (2.7 kPa). The residue obtained is purified by chromatography on a column of silica gel (particle size 0.06-0.20 mm), eluting with a mixture of cyclohexane and ethyl acetate (90/10 then 80/20 by volume). 19 g of (3aRS,7aSR)-2-benzyl-7,7-dimethoxy-2,3,3a, 4,7,7a -hexahydro-1H-4-isoindolone are obtained in oil form.

Provenance & Evidence