The first isolation and crystal structure of a boron difluoro complex (isoflavone yellow). Biologically active intermediates produced during isoflavone synthesis

The yellow intermediate 4f produced during the reaction of the deoxybenzoin 3f with N,N'-dimethyl(chloromethylene)ammonium chloride in the presence of BF3. Et2O prior to the formation of the corresponding isoflavone was isola ted for the first time and characterized by NMR, MS and single-crystal X-ra y diffraction techniques. These yellow intermediates showed anticancer, nem aticidal and mosquitocidal activities.