title: Preparation and X-ray crystal study of benziodoxaborole derivatives: new hypervalent iodine heterocycles.
abstract: A series of heterocyclic compounds containing trivalent iodine, oxygen, and boron in a five-membered ring were prepared and structurally investigated by X-ray crystallography. 1-Chloro-4-fluoro-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol was synthesized by chlorination of 2-fluoro-6-iodophenylboronic acid followed by treatment of the intermediate iododichloride with water. 1-Acetoxy-4-fluoro-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol, 1-acetoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol, and similar 1-substituted trifluoroacetate derivatives of benziodoxaborole were prepared the hypochlorite oxidation of 2-fluoro-6-iodophenylboronic acid or 2-iodophenylboronic acid in acetic or trifluoroacetic acid, respectively. 1-Acetoxy substituted benziodoxaborole can be further converted to the respective trifluoroacetate by treatment with trifluoroacetic acid or to the 1-hydroxy derivative by basic hydrolysis with aqueous NaHCO(3). X-ray structural studies of 1-chloro- and 1-trifluoroacetoxy substituted benziodoxaboroles 13, 17, and 18 have shown the presence of a planar five-membered heterocyclic ring with unusually short endocyclic I-O bond distance of 2.04-2.09 Å. Slow crystallization of 4-fluoro-1-trifluoroacetoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol from methanol resulted in the formation of a tetrameric macrocyclic structure 21 resulting from self-assembly of the initially formed 4-fluoro-1,3-dimethoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol. Structural parameters of the five-membered iodoxoborol ring, such as the planar geometry and the short B-O and O-I bonds lengths in 13, 17, and 18 compared to those in 21 and known benziodoxoles are indicative of partially aromatic character of this ring. Density functional theory (DFT) predicted NIST (0) and NIST (1) indexes for 1-chloro- and 1-trifluoroacetoxy substituted benziodoxaboroles, however, are indicative of significantly lower aromaticity compared to the classic aromatic systems.
authors: Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1039 University Dr., Duluth, Minnesota 55812, USA. vnemykin@d.umn.edu
authors: Victor N
authors: VN
authors: Nemykin
authors: Andrey V
authors: AV
authors: Maskaev
authors: Margarita R
authors: MR
authors: Geraskina
authors: Mekhman S
authors: MS
authors: Yusubov
authors: Viktor V
authors: VV
authors: Zhdankin
mesh_terms: D001896:Boron Compounds / Q000032:analysis / Q000138:chemical synthesis*; D015392:Chemistry, Inorganic / Q000379:methods*; D018360:Crystallography, X-Ray; D055772:Green Chemistry Technology / Q000379:methods*; D054879:Halogenation; D006576:Heterocyclic Compounds, 4 or More Rings / Q000032:analysis / Q000138:chemical synthesis*; D006997:Hypochlorous Acid / Q000737:chemistry; D007455:Iodine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D016877:Oxidants / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory; D014269:Trifluoroacetic Acid / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D001896:Boron Compounds; D006576:Heterocyclic Compounds, 4 or More Rings; D016877:Oxidants; D014867:Water; D006997:Hypochlorous Acid; D007455:Iodine; D014269:Trifluoroacetic Acid; D010100:Oxygen