5-Endo-dig electrophilic cyclization of 1,4-disubstituted but-3-yn-1-ones:: Regiocontrolled synthesis of 2,5-disubstituted 3-bromo- and 3-iodofurans

5-Endo-digelectrophilic cyclization of 1,4-diaryl but-3-yn-1-ones with N-bromosuccinimide or N-iodosuccinimide/acetone and iodine monochloride/ CH2CL2, at room temperature, in the absence of base, provides 3-halo-2,5-diarylfurans with excellent regiocontrol and high yields (81-94%).