Réactions de Friedel et Crafts de dérivés aromatiques sur les composés dioxo‐1,4,2,3‐non saturés. IV. Réactions des hydroxy‐5‐ouchloro‐5‐diméthyl‐3,5‐ ou diméthyl‐4,5‐dihydro‐2,5‐furannones‐2

Friedel‐Crafts reactions of aromatic derivatives with 1,4‐dicarbonyls 2,3‐éthylenic compounds. Part IV. Reactions of 5‐hydroxy or 5‐chloro 3,5‐dimethyl or 4,5‐dimethyl 2 (5 H) furanones We studied the Friedel‐Crafts reactions of 2‐(5 H )‐furanones. In the presence of sulfuric acid and of an aromatic derivative, 5‐hydroxy‐ or 5‐chloro‐5‐methyl‐2‐(5 H )‐furanones with one methyl group either in the 3 position, or in the 4 position generally give the corresponding 5‐aryl‐2‐(5 H )‐furanones, while with aluminium chloride, it is possible to obtain, when a reaction takes place, isomeric 1 H ‐indenecarboxylic acids. However, in a particular case, an addition to the substrate's double bond is observed. The 3‐aryl‐5‐hydroxy‐tetrahydrofuran‐2‐one obtained is methylated in two ways and gives either a cyclic product, or a linear one. In two cases tautomerism between 1 H ‐1‐indenecarboxylic acid and 1 H ‐3‐indenecarboxylic has been shown by 1 H‐NMR.