Benzofurans. Improved syntheses of bufuralol, 7-ethyl-2-(2-tert-butylamino-1-hydroxyethyl)benzofuran,and 1″-oxobufuralol, 7-acetyl-2-(2-tert-butylamino-1-hydroxyethyl)benzofuran

An improved laboratory scale synthesis of bufuralol ( 1 ) and 1″-oxobufuralol ( 4 ) was accomplished. The intermediate benzofurans were prepared via aromatization of 2,3-dihydrobenzofurans or by a one-step acidcatalyzed cyclization from 2,2-diethoxyethyl 4-bromo-6-ethyl-2-formylphenyl ether ( 23 ). Base-catalyzed cyclization of 3-(5-bromo-3-ethyl-2-hydroxyphenyl)-1.2-epoxypropane ( 16 ) provided the key intermediate, 5-bromo-7-ethyl-2-hydroxymethyl-2,3-dihydrobenzofuran ( 17 ). Selective functionalization of the C-2 and C-7 positions of the benzofuran ring system was accomplished to afford both 1 and 4 .