5-<i>Endo</i>-<i>D</i><i>ig</i> Electrophilic Cyclization of 1,4-Disubstituted But-3-yn-1-ones:  Regiocontrolled Synthesis of 2,5-Disubstituted 3-Bromo- and 3-Iodofurans

Abstract

[reaction: see text] 5-Endo-dig electrophilic cyclization of 1,4-diaryl but-3-yn-1-ones with N-bromosuccinimide or N-iodosuccinimide/acetone and iodine monochloride/CH(2)Cl(2), at room temperature, in the absence of base, provides 3-halo-2,5-diarylfurans with excellent regiocontrol and high yields (81-94%).