Synthesis of end‐functionalized polyethers by phosphazene base‐catalyzed ring‐opening polymerization of 1,2‐butylene oxide and glycidyl ether

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ⁵,4Λ⁵‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ⁵,4Λ⁵‐catenadi(phosphazene) (t‐Bu‐P₄), was confirmed. Among these superbases, only t‐Bu‐P₄ showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P₄‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P₄ system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P₄‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Photoredox‐Catalyzed Alkenylation of Benzylsulfonium Salts

Visible light‐mediated radical alkenylation of benzylsulfonium salts was achieved by means of fac‐Ir(ppy)₃ as a photocatalyst, giving allylbenzenes as products. A variety of functional groups, such as halogen, ester, and cyano, were well tolerated in this transformation. Starting benzylsulfonium salts could be readily prepared from benzyl alcohols by an acid‐mediated substitution, increasing the synthetic utility of this transformation.     

Nickel metallisation of Si by dynamic ion-beam mixing

Abstract

Thin Ni films were prepared at room temperature by Ni metal vapour deposition and simultaneous irradiation by Ar ions with an energy of 2–20 keV. The reaction of Ni with Si during dynamic ion-beam mixing was studied. The fluences of the ion beam were 4.7 × 10¹⁷ and 8.9 × 10¹⁷ cm^?2, and arrival rate ratios Ni/Ar were 9.7 and 5.1. Concentration profiles of Ni, Si, C, and O were analysed with Auger electron spectroscopy; the surface morphology and the crystalline structure were investigated with a cross-sectional scanning electron microscope and X-ray diffractometry. The theoretical profiles were calculated with the dynamic Monte Carlo simulation T-DYN for comparison with the experimentally obtained profiles. It was possible to observe the ballistic mixing effects and also thermally activated formation of nickel silicide.     

Total synthesis of pleurolactone

The stereoselective total synthesis of pleurolactone has been accomplished in 7 steps. The key synthetic features were the construction of four contiguous stereocenters using an endo-selective Diels-Alder reaction and high diastereoselective dihydroxylation.     

Gas Storage in Single-Walled Carbon Nanotubes

Abstract

X-ray diffraction (XRD) and electrical resistance measurement on single-walled carbon nan-otube (SWNT) samples prepared by the arc-discharge method are reported. The XRD profile of heat-treated sample indicated that air (oxygen, and/or nitrogen and/or water) can be condensed inside the SWNTs. We also found that the electrical resistance of SWNT soot is significantly affected by exposing to the oxygen gas and humid air.