Synthesis of 6- and 7-alkoxy-4-methylcoumarins from corresponding hydroxy coumarins and their conversion into 6- and 7-alkoxy-4-formylcoumarin derivatives

Abstract

Hydroxy derivatives of 4-methyl-2H-chromen-2-one were prepared from hydroquinone and resorcinol through their reaction with ethyl acetoacetate. These hydroxy coumarins were then converted into corresponding alkoxy derivatives by reaction with alkyl halides. The yields of 6- and 7-alkoxy-4-methylcoumarins 3a–i and 4a–i were 55−95%. Oxidation of these compounds by selenium dioxide under conventional and microwave-assisted heating conditions produced corresponding 4-formyl compounds 5b–h and 6b–h with yields of 40−67% and 90−93%, respectively. Several 6- and 7-alkoxy-4-methylcoumarins 3a–i, 4a–i and nearly all 6- and 7-alkoxy-4-formylcoumarins 5b–h, 6b–h are novel compounds.