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Paper | Regular issue | Vol 27, No. 4, 1988, pp.955-959
Published online, 1st January, 1970
DOI: 10.3987/COM-87-4447
Remote Induction of the Condensation of p-Nitrobenzaldehyde on the Methylene Group of 5-Hydroxy-2-coumaranone

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


(Z)-5-Hydroxy-3-(p-nitrobenzylidene)-2-coumaranone ((Z)-p-nitromarginalin) is obtained in 92% yield by reaction of p-nitrobenzaldehyde with 5-hydrony-2-coumaranone. The same condensation carried out with 2-coumaranone gives a mixture of (Z)- and (E)-p-nitrobenzylidene-2-caumaranones (72% yield) in a 2:1 ratio. In a discussion taking also into account previous results in the series, it is concluded that the 5-hydroxyl group exerts a remote induction in the orientation of the intermediate secondary alcohol, stabilized through chelation with the lactone carbonyl group. Such a long distance effect is in agreement with the requirements of the Cram’s rule, leading in this particular case to a high stereoselectivity in the final dehydrated ene-lactone.