Synthesis and Crystal Structure of (μ-Malonanilide-<i>O</i>,<i>O</i>‘)bis[bis(dibenzoylmethanato)dioxouranium(VI)]: A New Coordination Mode of the Malonamide Ligand

Synthesis and Crystal Structure of (μ-Malonanilide-O,O‘)bis[bis(dibenzoylmethanato)dioxouranium(VI)]:  A New Coordination Mode of the Malonamide Ligan

Synthesis and Crystal Structure of (μ-Malonanilide-<i>O</i>,<i>O</i>‘)bis[bis(dibenzoylmethanato)dioxouranium(VI)]: A New Coordination Mode of the Malonamide Ligand

Synthesis and Crystal Structure of (μ-Malonanilide-O,O‘)bis[bis(dibenzoylmethanato)dioxouranium(VI)]:  A New Coordination Mode of the Malonamide Ligan

Functionalization of <i>p-tert</i>-Butylcalix[5]arene by Alkylation with 2-(Chloromethyl)pyridine Hydrochloride

A study of the base-catalyzed alkylation of p-tert-butylcalix[5]arene (1) with 2-(chloromethyl)pyridine hydrochloride (PicCl·HCl) in DMF has led to the isolation and identification of the 7 possible pyridinyl homologues of 1 in the cone conformation. Reactions of 1 with limiting amounts of alkylating agent (2 to 4 equiv) and base (CsF, KHCO3, BaO/Ba(OH)2, K2CO3, NaH) produced invariably complex mixtures, which were separated into the pure components by chromatographic means. Regioselective 1,2,4- or 1,2,3-tri-O-alkylation has been achieved in moderate yield (21−22%) by an appropriate choice of molar ratios, solvent, and base. Pentaethers 8−10, endowed with 2-pyridinyl, 3-pyridinyl, and 2-quinolylmethyl pendant groups at the lower rim, respectively, have been also prepared in good yield. The cone conformation in solution for all new compounds has been established by NMR spectroscopy and confirmed for 1,2,3-tri-O-alkylated 5 by a single-crystal X-ray analysis. In the solid state the cone conformation of 5 is mainly determined by the presence of intramolecular hydrogen bonds between adjacent phenolic oxygens, and between the phenolic oxygen and the proximal pyridinyl nitrogen

Enantioselective Construction of Cyclic Ethers by An Aldol-Cyclization Sequence

We have modified the substrate used in deconjugative aldol-cyclizations by incorporating the Evans chiral auxiliary. The deconjugative aldol step, using boron enolates, gave the expected products with complete syn-aldol stereochemistry. These compounds could then undergo an iodine-mediated cyclization to form optically active products. Oxetanes and fused ring tetrahydrofurans were easily assembled with a variety of substitution patterns and with excellent enantiocontrol. The deconjugation of acyclic chiral enimides resulted in the loss of control of olefin geometry. However, these compounds did appear to cyclize with excellent enantiocontrol

Successive Photosubstitution of Hexachlorobenzene with Cyanide Ion

We report a novel nucleophilic polysubstitution reaction of hexachlorobenzene (HCB) with cyanide ion in acetonitrile/water. Successive photocyanations of HCB occur with high quantum yield (φdiss → 0.18) without the need for an electron acceptor, to give as products pentacyanophenol, 4-chloro-2,3,5,6-tetracyanophenol, and a dichlorotricyanophenol. The phenol functional group is introduced by competing hydrolysis of the polycyanochlorinated benzenes. Sensitization and quenching experiments indicate a triplet reactive excited state. Variation of [CN-] at constant [HCB] follows the expected relationship φdiss −1 ∝ [CN-]-1, but variation of [HCB] at constant [CN-] shows that the reaction becomes less efficient with increasing [HCB], consistent with the formation of an unproductive excimer

Multinuclear NMR Spectroscopic and X-ray Crystallographic Studies of a Series of Mercury(II) Complexes Containing the Bidentate Phosphine Ligand Ph₂PCH₂Si(CH₃)₂CH₂PPh₂ (L²)

The bidentate phosphine ligand Ph2PCH2Si(CH3)2CH2PPh2 (L2), an analogue of 1,3-bis(diphenylphosphino)propane (dppp), coordinates to mercury(II) salts to form complexes of the general formula [HgX2·L2] (X = Cl, Br, I, NCS). Infrared, Raman, and multinuclear (1H, 13C, 31P, 199Hg) NMR spectroscopic studies show that the complexes exhibit four-coordinate pseudotetrahedral metal geometry. [HgI2(Ph2PCH2Si(CH3)2CH2PPh2)] (1) crystallizes in the monoclinic space group P21/n with a = 13.028(2) Å, b = 17.402(5) Å, c = 13.849(2) Å, β = 90.635(14)°, V = 3139.5(11) Å3, and Z = 4. The structure contains a tetrahedral mercury center with the phosphine ligand bound in a bidentate fashion:  Hg−P 2.511(2), 2.515(2) Å; P−Hg−P 105.28(6)°. The complex [HgCl2]2·L2 has also been generated via a 2:1 metal:phosphine stoichiometry

Mechanism and Stereochemistry of the Reaction of Dichloroplatinum(II) Complexes with Diazo Compounds. X-ray Structures of Four Key Products: [(2<i>R,</i>3<i>R</i>)-Bis(diphenylphosphino)butane]chloro- [(<i>S</i>)-chloro(methoxycarbonyl)methyl]platinum(II), (η⁴-1,5-Cyclooctadiene)[3-chloro-5-(dimethoxyphosphonyl)-2- methoxy-4,1,2-platinaoxaphospholane <i>P</i>-oxide], (<i>R,R)</i>-[Chloro(dimethoxyphosphonyl)methyl][chloro- (trimethylsilyl)methyl](1,5-cyclooctadiene)platinum(II), and Chloro[chloro(dimethoxyphosphonyl)methyl](η⁴-1,5-cyclooctadiene)platinum(II)

The structures of four key products formed by reaction of diazo compounds of the type RCHN2 (R = CO2Me, P(O)(OMe)2, SiMe3) with chloroplatinum(II) derivatives have been elucidated by X-ray crystallographic methods. The results confirm our earlier conclusions, based on NMR evidence and mechanistic considerations, concerning the stereochemistries of these products

Sterically Hindered and Robust Pnictogen Ligands Derived from Carboranes: Synthesis and X-ray Structure Determination of Tris(1‘-methyl(1,2-dicarba-<i>c</i><i>loso</i>-dodecaboran-1-yl))phosphine, Tris(1‘-methyl(1,2-dicarba-<i>c</i><i>loso</i>-dodecaboran-1-yl))arsine and Chloro(Tris(1‘-methyl(1,2-dicarba-<i>c</i><i>loso</i>-dodecaboran-1-yl))phosphine)gold(I)

Sterically hindered phosphine and arsine ligands derived from ortho-carborane were synthesized and characterized by X-ray crystallography. Tris(1‘-methyl(1,2-dicarba-closo-dodecaboran-1-yl))phosphine, 2 (crystal data, hexagonal, space group P63, a = b = 12.251(3) Å, c = 11.514(4) Å, α = β = 90°, γ = 120°, V = 1496.6(7) Å3, Z = 2, R1 = 0.0568) and tris(1‘-methyl(1,2-dicarba-closo-dodecaboran-1-yl))arsine, 3 (crystal data, hexagonal, space group P63, a = b = 12.330(3) Å, c = 11.474(4) Å, α = β = 90°, γ = 120°, V = 1510.7(7) Å3, Z = 2, R1 = 0.0930) were prepared in 82% and 68% yield, respectively. The phosphine ligand is resistant to air-oxidation but was converted to corresponding oxide when heated with hydrogen peroxide. The tertiary carboranyl phosphine reacted with (Tht)AuCl to yield chloro(tris(1‘-methyl(1,2-dicarba-closo-dodecaboran-1-yl))phosphine)gold(I), 4 (crystal data, monoclinic, space group P21/c, a = 19.101(4) Å, b = 12.167(2) Å, c = 13.846(3) Å, α = γ = 90°, β = 91.13(3)°, V = 3217.2(11) Å3, Z = 4, R1 = 0.0396) in 82% yield. From the X-ray structure of the gold complex, the cone angle of the phosphine was determined to be 213(2)°, which is among the largest values reported to date

Sterically Hindered and Robust Pnictogen Ligands Derived from Carboranes: Synthesis and X-ray Structure Determination of Tris(1‘-methyl(1,2-dicarba-<i>c</i><i>loso</i>-dodecaboran-1-yl))phosphine, Tris(1‘-methyl(1,2-dicarba-<i>c</i><i>loso</i>-dodecaboran-1-yl))arsine and Chloro(Tris(1‘-methyl(1,2-dicarba-<i>c</i><i>loso</i>-dodecaboran-1-yl))phosphine)gold(I)

Sterically hindered phosphine and arsine ligands derived from ortho-carborane were synthesized and characterized by X-ray crystallography. Tris(1‘-methyl(1,2-dicarba-closo-dodecaboran-1-yl))phosphine, 2 (crystal data, hexagonal, space group P63, a = b = 12.251(3) Å, c = 11.514(4) Å, α = β = 90°, γ = 120°, V = 1496.6(7) Å3, Z = 2, R1 = 0.0568) and tris(1‘-methyl(1,2-dicarba-closo-dodecaboran-1-yl))arsine, 3 (crystal data, hexagonal, space group P63, a = b = 12.330(3) Å, c = 11.474(4) Å, α = β = 90°, γ = 120°, V = 1510.7(7) Å3, Z = 2, R1 = 0.0930) were prepared in 82% and 68% yield, respectively. The phosphine ligand is resistant to air-oxidation but was converted to corresponding oxide when heated with hydrogen peroxide. The tertiary carboranyl phosphine reacted with (Tht)AuCl to yield chloro(tris(1‘-methyl(1,2-dicarba-closo-dodecaboran-1-yl))phosphine)gold(I), 4 (crystal data, monoclinic, space group P21/c, a = 19.101(4) Å, b = 12.167(2) Å, c = 13.846(3) Å, α = γ = 90°, β = 91.13(3)°, V = 3217.2(11) Å3, Z = 4, R1 = 0.0396) in 82% yield. From the X-ray structure of the gold complex, the cone angle of the phosphine was determined to be 213(2)°, which is among the largest values reported to date

Mechanism and Stereochemistry of the Reaction of Dichloroplatinum(II) Complexes with Diazo Compounds. X-ray Structures of Four Key Products: [(2<i>R,</i>3<i>R</i>)-Bis(diphenylphosphino)butane]chloro- [(<i>S</i>)-chloro(methoxycarbonyl)methyl]platinum(II), (η⁴-1,5-Cyclooctadiene)[3-chloro-5-(dimethoxyphosphonyl)-2- methoxy-4,1,2-platinaoxaphospholane <i>P</i>-oxide], (<i>R,R)</i>-[Chloro(dimethoxyphosphonyl)methyl][chloro- (trimethylsilyl)methyl](1,5-cyclooctadiene)platinum(II), and Chloro[chloro(dimethoxyphosphonyl)methyl](η⁴-1,5-cyclooctadiene)platinum(II)

The structures of four key products formed by reaction of diazo compounds of the type RCHN2 (R = CO2Me, P(O)(OMe)2, SiMe3) with chloroplatinum(II) derivatives have been elucidated by X-ray crystallographic methods. The results confirm our earlier conclusions, based on NMR evidence and mechanistic considerations, concerning the stereochemistries of these products