Synthetic experiments in the benzo-pyrone series. Part XVII. Some isoflavono-7 : 8-furans

Abstract

Two methods of synthesising isoflavonofurans of the angular type are examined. Starting from karanjic acid (VI) and passing through the intermediate (X), 2-methyl-isoflavono-7 : 8-furan (XI) is easily obtained. The alternative method which starts with 2-methyl-7-hydroxy-isoflavone (XII) and builds up the furan ring through the 8-aldehyde (XIII) is beset with difficulties. However if instead of the aldehyde, the corresponding ketone (8-acetyl derivative XVII) is employed the difficulties are eliminated and good yield of 2 : β-dimethyl-isoflavono-7 : 8-furan (XIX) is secured.