lsocoumarins : Part VIII-Synthesis of 6, 7-Dimethoxy-3-Alkyllsocoumarins

Pyridine catalysed reactions of 4,5-dimethoxyhomophthalic acid with acetic and propionic anhy­drides at room temperature gave 4-acetyl- and 4-propionyl-6,7-dimethoxyisochroman-1,3-diones respec­tively and at boiling water bath temperature gave 3-methyl- and 3-ethyl-4-carboxy-6,7dirnethoxyisocou­marins respectively, along with other products. The rearrangement of the acetyl and propionylisoclu'o­mancliones to the 3-methyl- and 3-ethyl-4-carboxyisocoumarins respectively, was accomplished with H2SO4. The study of the various other reactions have led to the synthesis of 6,7-dimethoxy-3-alkyliso­coumarins and 3,4-di-hydroisocoumarins and also of 2-carboxy-4,5-dimethoxybenzyl alkyl ketones in goad yields