Syntheses and Br•••π supramolecular interactions in the crystal structure of ipriflavone bromides

Two novel compounds, 3,8-dibromo-2-methoxyl-7-isopropoxyisoflavanone (1) and 3,6-dibromo-2-methoxyl-7-isopropoxyisoflavanone (2), are synthesized via bromination reaction of their precursor ipriflavone in methanol. The mixture of 1 and 2 co-crystallizes in ethanol and forms two different crystal shapes, the shape of 1 being block and 2 prism, they can be separated manually. 1 and 2 are characterized by IR, H-1 NMR and single crystal X-ray diffraction. The mechanism of bromination reaction is also discussed. 1 crystallizes in the monoclinic space group P 2(1)/n with cell parameters a = 1.3569(3) nm, b = 0.6706(2) nm, c = 2.0704(4) nm, beta = 97.50(2)degrees, V= 1.8678(6) nm(3), Z = 4, Dc = 1.672 Mg/m(3), R = 0.0455, wR = 0.0779, F(000) = 936. 2 crystallizes in the monoclinic space group P 2(1)/c with cell parameters a =1.3854(17) nm, b = 1.1215(14) nm, c = 1.3038(17) nm, beta = 103.71(2)degrees, V= 1.968(4) nm(3), Z = 4, Dc = 1.587 Mg/m(3), R = 0.0306, wR = 0.0619, F(000) = 936. The Br...pi interactions, hydrogen bonds, aromatic hydrogen bonds and aromatic stacking interactions exist in the crystal structures of 1 and 2, which lead them into supramolecular compounds with a three-dimensional network structure, respectively. 1 and 2 are the isoflavanone derivatives halogenated at C3 and this kind of isoflavanone halides has not been reported yet.