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Paper | Regular issue | Vol 26, No. 2, 1987, pp.421-425
Published online, 1st January, 1970
DOI: 10.3987/R-1987-02-0421
Direct Access to 4-Substituted 3-Isochromanones by the pH Controlled Addition of Aldehydes

Michel Barbier

*Institut des Chimie des Substances Naturelles, C.N.R.S., 1 avenue de la Terrasse, Bat. 27, 91198 Gif-sur-Yvette Cedex, France

Abstract

Aldehydes condense at position 4 of 3-isochromanone in the presence of a base, in competition with the ring opening of the lactone. By control of the pH, the new syn and anti 4-ethyliaene and benzylidene derivatives are obtained with yields of 30 and 28%. Due to the strong interaction of the olefinic proton with the carbonyl group of the lactone, in particular in the case of the stilbene structures prepared through reaction with a benzaldehyde, these syn and anti isomers are easily resolved by chromatography and characterized. The 4-methylene 3-isochromanone obtained through addition of formaldehyde is not stable and polymerizes readily to a mixture of polymers.