濃オルト燐酸によるカルコンのフラバノン閉環 (第2報)

フロログルシンモノメチルエーテル系カルコン類の閉環

抄録

2′, 4′-Dihydroxy-4, 6′-dimethoxychalcone and its 3′-methyl derivative afforded 4′, 5-dimethoxy-7-hydroxy-flavanone and its 8-methyl derivative in a good yield on heating with conc. phosphoric acid for a few minutes on a water bath. However, condensation of 2, 6-dihydroxy-3-methyl-4-methoxyacetophenone and anisaldehyde did not afford 2′, 6′-dihydroxy-3′-methyl-4, 4′-dimethoxychalcone but formed 4′, 7-dimethoxy-5-hydroxy-8-methylflavanone, that it was not possible to examine the action of conc. phosphoric acid on this chalcone. The methylation of the flavanones hereby obtained with dimethyl sulfate did not afford the completely methylated compound but gave 2′-hydroxy-3′-methyl-4, 4′, 6′-trimethoxychalcone and its completely methylated compound.