Methoxycarbonyltrifluoromethylthioketene

A new method was developed for the synthesis of methoxycarbonyltrifluoromethylthioketene by thermal cleavage of tert-butyl 1,3,3,3-tetrafluoro-2-methoxycarbonylpropenyl sulfide in the presence of P₂O₅. This thioketene was demonstrated to exhibit high reactivity in reactions with nucleophiles as well as in ene and diene syntheses.     

Investigation of the scope and mechanism of copper catalyzed regioselective methylthiolation of aryl halides

Methylthiolation of structurally diverse aryl halides was accomplished under fluoride free conditions using catalytic amounts of CuI, and DMSO as the methylthiolation source. Optimization studies unveiled several varieties of promoters among which Zn(OAc)₂ was found ideal. The analogous reaction with DMSO-d₆ afforded corresponding deuterated aryl methyl thioether with 99% purity. Mechanistic studies revealed CuSMe as the active methylthiolation agent.     

Cu(I)/Chiral Bisoxazoline-Catalyzed Enantioselective Doyle-Kirmse Reaction of Allenyl Sulfides with α-Diazoesters

Herein, a Cu(I)-catalyzed enantioselective Doyle-Kirmse reaction of allenyl sulfides and α-diazoesters is reported, which provides an efficient synthetic route to enantio-enriched chiral tertiary homopropargylic sulfides. This reaction features high enantioselectivities (up to 96 % ee) and good functional group tolerance. The alkyl substituted α-diazoester has also been demonstrated as the efficient substrates in the asymmetric Doyle-Kirmse reaction. Mechanistic studies, including kinetic experiments, were conducted to gain insights into the details of the reaction pathway. The potential synthetic utility of this protocol has also been demonstrated.     

FORMATION AND GC-MS CHARACTERIZATION OF UNUSUAL CYCLIC SULFIDES

Abstract

connection with another project involving the cleavage of the thiirane ring of cyclohexene episulfide in the presence of trifluoromethylthiocopper, the presence of several unusual cyclic sulfides (5–10, Fig. 1) was observed both in the reaction product and the starting material itself. The formation of these compounds has been rationalized on the presence and participation of the thiyl radical species. Details pertaining to their formation and characterization based on their mass spectral fragmentation behavior are presented in this communication.     

HETEROCYCLIC SULFUR COMPOUNDS LXXXIV: 3-Alkoxy-1,2-dithio-isocoumarins and 3-Alkylthio-1,2-dithio-isocoumarins

Abstract

Reaction of phosphorus pentasulfide with alkyl hydrogen homophthalates or dialkyl homophthalates gives a mixture of 3-alkoxy-1,2-dithio-isocoumarins and of 3-alkylthio-1,2-dithio-isocoumarins; some of these compounds resulting from a migration of an alkoxy or of an alkylthio group.

Oxidation of these dithio-isocoumarins into 2-thio-isocoumarins has been performed either by potassium permanganate or by benzonitrile N-oxide.     

Zirconium oxide complex anchored on boehmite nanoparticles as highly reusable organometallic catalyst for C–S and C–O coupling reactions

Boehmite nanoparticles were prepared by a simple and inexpensive procedure in water using commercially available materials without inert atmosphere. Then, the surface of the boehmite nanoparticles was modified using 3‐mercaptopropyltrimethoxysilane and subsequently zirconium oxide was supported on the modified surface. Zirconium oxide supported on boehmite nanoparticles (Pr.S‐ZrO@boehmite) was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and inductively coupled plasma technique. The catalytic application of Pr.S‐ZrO@boehmite was studied in C–O and C–S coupling reactions for synthesis of valuable compounds such as ether and sulfide derivatives. All products were obtained in good to excellent yields and the catalyst could be recovered and reused several times without significant loss of catalytic efficiency. Furthermore, zirconium oxide is rarely used as catalyst for cross‐coupling reactions.     

New chiral Schiff bases derived from (+)- and (−)-α-pinenes in the metal complex catalyzed asymmetric oxidation of sulfides

New chiral Schiff bases were derived from (+)- and (−)-α-pinenes for the first time. Coordinated to vanadium ions, they can be used as ligands in catalytic oxidation of sulfides into chiral sulfoxides. Conditions for the asymmetric oxidation of thioanisole to methyl phenyl sulfoxide in optical purity up to 32% were found. Variation of substituents in the ligand has a significant effect not only on enantioselectivity of the reaction, but also on absolute configuration of the sulfoxide formed. Dedicated to Academician G. A. Tolstikov in honor of his 75th anniversary. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 105–113, January, 2008.     

Electronic and optical properties of ZnSc2S4 and CdSc2S4 cubic spinels by the modified Becke–Johnson density functional

Structural, electronic and optical properties of the ZnSc₂S₄ and CdSc₂S₄ cubic spinels have been investigated by means of the full-potential (linearized) augmented plane wave plus local orbitals based on density functional theory. The exchange-correlation potential is treated by the GGA–PBEsol [J.P. Perdew, A. Ruzsinszky, G.I. Csonka, O.A. Vydrov, G.E. Scuseria, L.A. Constantin, X. Zhou, K. Burke, Phys. Rev. Lett. 100 (2008) 136406] and the recently proposed modified Becke–Johnson potential approximation (mBJ) [F. Tran, P. Blaha, Phys. Rev. Lett. 102 (2009) 226401], which successfully corrects the band-gap problem found with GGA for a wide range of materials. The obtained structural parameters are in good agreement with the available experimental data. This gives support for the predict properties for ZnSc₂S₄ and CdSc₂S₄. The band structures reveal that both compounds are semiconductor with a direct gap. The obtained gap values show that mBJ is superior for estimating band gap energy. We have calculated the electron and hole effective masses in different directions. The density of states has been analyzed. Based on our electronic structure obtained using the mBJ method we have calculated various optical properties, including the complex dielectric function ɛ(ω), complex index of refraction n(ω), reflectivity coefficient R(ω), absorption coefficient α(ω) and electron energy-loss function L(ω) as functions of the photon energy. We find that the values of zero-frequency limit ɛ₁(0) increase with decreasing the energy band gap in agreement with the Penn model. The origin of the peaks and structures in the optical spectra is determined in terms of the calculated energy band structures.     

Functionalization of a Single C−F Bond of Trifluoromethylarenes Assisted by an ortho-Silyl Group Using a Trityl-Based All-in-One Reagent with Ytterbium Triflate Catalyst

Catalytic thiolation and azidation of a single C−F bond of trifluoromethylarenes were achieved assisted by an ortho-silyl group with all-in-one reagents to generate a trityl cation and nucleophiles. The reactions catalyzed by ytterbium triflate efficiently afforded a wide variety of difluoromethylenes avoiding the further C−F bond cleavage, by virtue of the mild conditions without the generation of a Brønsted acid.     

High Performance Bifunctional Electrocatalysts Designed Based on Transition-Metal Sulfides for Rechargeable Zn–Air Batteries

Due to the energy crisis by the excessive consumption of fossil fuels, Zinc–air batteries (ZABs) with high theoretical energy density have attracted people‘s attention. The overall performance of ZABs is largely determined by the air cathode catalyst. Therefore, it is necessary to develop high-efficiency and low-cost bifunctional catalysts to replace noble metal catalysts to promote the development of ZABs. Among a variety of cathode catalysts, TMS has become a research hotspot in recent years because of its better electrical conductivity than metal phosphides and metal oxides. In this work, we focus on the means of improving the electrocatalytic performance of transition-metal sulfides (TMS) providing ideas for us to rationally design high-performance catalysts. Furthermore, the performance improvement law between catalyst performance and ZABs is also discussed in this work. Finally, some challenges and opportunities faced in the research of TMS electrocatalysis are briefly proposed, and strategies for improving the performance of ZABs are prospected.