Iridium-Catalyzed Hydrosilylation of Sulfur-Containing Olefins

Hydrosilylation of various sulfur-containing olefins with (RO)₃SiH has been achieved using iridium catalysts [IrX­(cod)]₂ (X = Cl, SPh). The catalysis is applicable to the chemoselective hydrosilylation of thioacetate, which enables the preparation of an industrially important silane coupling agent

Highly Selective Synthesis of Hydrosiloxanes by Au-Catalyzed Dehydrogenative Cross-Coupling Reaction of Silanols with Hydrosilanes

We report a highly selective synthesis of siloxane building blocks containing <i>SiH</i>₂ <i>or SiH</i> functionalities. AuCl­(PPh₃)/PPh₃ or AuCl­(PPh₃)/P^<i>n</i>Bu₃ system catalyzed the reaction of trihydrosilanes with silanols giving <i>SiH</i>₂-containing siloxanes exclusively. On the other hand, a highly selective reaction of dihydrosilanes with silanols to afford <i>SiH</i>-containing siloxanes was achieved by simply changing the phosphine ligand to a bidentate one, xantphos. Usefulness of <i>SiH</i>₂-containing siloxanes was demonstrated by the synthesis of a trisiloxane, Et₃SiOSi­(Ph)­(H)­OSi^<i>t</i>BuMe₂, and a pentasiloxane, Ph₂Si­(OSiHPhOSiEt₃)₂, bearing <i>SiH</i> functionalities

Synthesis and Properties of Tellurinic Anhydride–Tellurone Adducts

The synthesis and characterization of stable tellurinic anhydride–tellurone adducts are reported. Treatment of aryltellurinic anhydride with diaryl tellurone gave pentacyclotelluroxane consisting of two molecules each of the starting tellurium oxides. The bulky aromatic substituents attached to the tellurium atoms efficiently prevent further aggregation and enable full characterization using multinuclear (¹H, ¹³C, and ¹²⁵Te) NMR and IR spectroscopy as well as elemental analysis. For (TipTe)₄(Tip₂Te)₂O₁₀ (<b>3TT</b>, Tip = 2,4,6-triisopropylphenyl), the molecular structure was unambiguously determined by an X-ray crystallographic analysis. To estimate the dissociation energies of the tellurinic anhydride–tellurone adducts, density functional theory calculations were performed, and it was found that the adducts are highly stabilized by forming a four di-μ-oxo bridge structure

Synthesis and Properties of Tellurinic Anhydride–Tellurone Adducts

The synthesis and characterization of stable tellurinic anhydride–tellurone adducts are reported. Treatment of aryltellurinic anhydride with diaryl tellurone gave pentacyclotelluroxane consisting of two molecules each of the starting tellurium oxides. The bulky aromatic substituents attached to the tellurium atoms efficiently prevent further aggregation and enable full characterization using multinuclear (¹H, ¹³C, and ¹²⁵Te) NMR and IR spectroscopy as well as elemental analysis. For (TipTe)₄(Tip₂Te)₂O₁₀ (<b>3TT</b>, Tip = 2,4,6-triisopropylphenyl), the molecular structure was unambiguously determined by an X-ray crystallographic analysis. To estimate the dissociation energies of the tellurinic anhydride–tellurone adducts, density functional theory calculations were performed, and it was found that the adducts are highly stabilized by forming a four di-μ-oxo bridge structure

Efficient Pd-Catalyzed Dehydrogenative Coupling of P(O)H with RSH: A Precise Construction of P(O)–S Bonds

A Pd-catalyzed dehydrogenative phosphorylation of thiols is developed. A variety of thiols dehydrogenatively couple readily with all three kinds of P­(O)–H compounds, i.e., H-phosphonates, H-phosphinates, and secondary phosphine oxides, providing a general access to the valuable phosphorothioates including the <i>P</i>-chiral compounds. A plausible mechanism is proposed

Direct Silyl–Heck Reaction of Chlorosilanes

A nickel complex/Lewis acid combination effectively catalyzed the direct silyl–Heck reaction of chlorosilanes, which are key raw materials in the organosilicon industry, to give synthetically important alkenylsilane products. Trichlorosilanes, dichlorosilanes, and monochlorosilanes underwent the silyl–Heck reaction to afford the corresponding alkenylsilanes in high yields. In the reactions of dichlorosilanes, a single substitution occurred to give monoalkenylsilanes in a highly selective manner

Acid-Catalyzed Condensation Reaction of Phenylsilanetriol: Unexpected Formation of <i>cis,trans</i>-1,3,5-Trihydroxy-1,3,5-triphenylcyclotrisiloxane as the Main Product and Its Isolation

<i>cis,trans-</i>1,3,5-Trihydroxy-1,3,5-triphenylcyclotrisiloxane was successfully isolated and fully characterized by spectroscopic methods and single-crystal X-ray diffraction. This compound was believed to be highly unstable and only exist as a transient species in low concentration during the condensation reaction of phenylsilanetriol or its precursors. The isolated pure cyclotrisiloxane is, however, surprisingly stable even in acidic solution and partially isomerizes to the <i>cis,cis</i> isomer

Hierarchical Structural Change in the Stress-Induced Phase Transition of Poly(tetramethylene terephthalate) As Studied by the Simultaneous Measurement of FTIR Spectra and 2D Synchrotron Undulator WAXD/SAXS Data

The simultaneous measurement of Fourier transform infrared (FTIR) transmission spectra and 2-dimensional wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) patterns has been performed successfully to investigate the hierarchical structure changes occurring in the stress-induced phase transition phenomenon of uniaxially oriented poly­(tetramethylene terephthalate) film. The molar fraction of the β-crystal form, evaluated from the IR and WAXD data analyses, increased steeply in the plateru region of the stress–strain curve as already known well. The 2D SAXS data have revealed the remarkable and reversible change in the stacked lamellar structure just after the α-to-β phase transition was completed, where the tilting angle of the stacked lamellae measured from the draw axis of the oriented sample became zero, and the lamellar thickness increased due to the inclusion of amorphous region located in the boundary part of the crystalline lamellae. In parallel, the X-ray reflection spots in a wider diffraction angle region became diffuse in the observed WAXD pattern of the β form, indicating the packing disorder of the mechanically stressed chains. In this way, the simultaneous combination of the 3 different types of equipments has allowed us to deduce the detailed structural change from the various levels: the stress-induced α–β transition was found to occur not only with the remarkable changes in the molecular chain conformation and chain packing mode in the crystal lattice, but also with the large and reversible change in the lamellar stacking structure. The stress-induced changes in lamellar thickness and long period were simulated using a mechanical model with these hierarchical structure changes taken into account, giving relatively good reproduction of the observed data