An efficient route for commercially viable syntheses of furan- and thiophene-anellated β-hydroxychalcones

An efficient route for the syntheses of β-hydroxychalcones containing benzofuran and benzothiophene rings is described. Isoxazolines obtained from oxime–olefin cycloadditions were reduced under pressure to a mixture of products. Isoxazoles obtained from Claisen aroylation of an ester and subsequent acid cyclization, or from isoxazolines via DDQ-mediated dehydrogenation, were subjected to catalytic hydrogenation followed by hydrolysis to afford 1-phenyl-3-(benzofuran-5-yl)-1,3-diketone and 1-phenyl-3-(benzothiophene-5-yl)-1,3-diketones in very good yields.