Synthesis of vinyl sulfides via hydrothiolation of alkynes using Al2O3/KF under solvent-free conditions

We present here a clean, solvent-free hydrothiolation of alkynes using solid supported catalyst (Al₂O₃/KF). This efficient and improved method selectively furnishes the corresponding anti-Markovnikov vinyl sulfides in good to excellent yields. The method is applicable for aliphatic and aromatic thiols and the catalytic system can be re-used up to two times without previous treatment and with comparable activity.     

离子液体BMIMBF4中对甲氧基甲苯的电化学氧化

以离子液体1-丁基-3-甲基咪唑四氟硼酸盐(BMIMBF4)为电解质,采用循环伏安法(CV)、计时电流法(CP)、原位傅里叶变换红外光谱(in situ FTIRS)法等手段研究了对甲氧基甲苯(p-MT)在铂电极上的电氧化行为.实验结果表明:对甲氧基甲苯在离子液体中的电化学氧化反应是受扩散控制的四电子不可逆过程,估算了其扩散系数D=3.4×10-7cm2.s-1,主要电氧化产物为茴香醛,加入适量的水或适当提高温度有利于电氧化反应向生成相应醛的方向进行.     

Addition of chalcogenolate anions to terminal alkynes using microwave and solvent-free conditions: easy access to bis-organochalcogen alkenes

We present here the reaction of diphenyl dichalcogenides (Se and Te) with propargyl alcohols using alumina supported sodium borohydride under solvent-free conditions. This efficient and improved method is general and furnishes the corresponding vinyl chalcogenide preferentially with a Z configuration. We also observed that when the same protocol was applied to phenyl acetylene, the (E)-bis-organochalcogen alkenes were obtained in good yields and high selectivity. The use of MW irradiation facilitates the procedure and accelerates the reaction.     

Syntheses and characterization of the actinide manganese selenides ThMnSe3 and UMnSe3

The AnMnSe₃ (An=Th, U) compounds were synthesized from high-temperature solid-state reactions of the constituent elements at 1223 and 1273 K, respectively. Both compounds are isostructural with UFeS₃ and crystallize in the space group Cmcm of the orthorhombic system with four formula units in a cell. Cell constants (Å) at 153 K are: ThMnSe₃, 4.0304(4), 12.795(1), 9.2883(9); UMnSe₃, 3.931(5), 12.705(14), 9.148(10). The structure comprises layers of MnSe₆ octahedra that alternate with layers of AnSe₈ bicapped trigonal prisms along the b-axis. Because there are no Se-Se bonds in the structure of AnMnSe₃ the formal oxidation states of An/Mn/Se are 4+/2+/2−. UMnSe₃ is a ferromagnet with T_C=62 K.     

Alkylation of toluene with 1,3-pentadiene catalyzed by [bupy]BF4-AlCl3 and [bupy]BF4-FeCl3 ionic liquids

A new application of ionic liquids is developed for a novel process of synthesizing pentyltoluene from toluene and a C5 diolefin (1,3-pentadiene). The catalyst [bupy]BF₄-AlCl₃ behaves better than [bupy]BF₄-FeCl₃.     

Palladium and platinum catalyzed hydroselenation of alkynes: SeH vs SeSe addition to CC bond

A mechanistic study of the hydroselenation of alkynes catalyzed by Pd(PPh₃)₄ and Pt(PPh₃)₄ has shown that the palladium complex gives products of both SeH and SeSe bond addition to the triple bond of alkynes, while the platinum complex selectively catalyzes SeH bond addition. The key intermediate of PhSeH addition to the metal center, namely Pt(H)(SePh)(PPh₃)₂, was detected by ¹H-NMR spectroscopy. The analogous palladium complex rapidly decomposes with evolution of molecular hydrogen. A convenient method was developed for the preparation of Markovnikov hydroselenation products H₂CC(SePh)R, and the scope of this reaction was investigated. The first X-ray structure of the Markovnikov product H₂CC(SePh)CH₂N⁺HMe₂·HOOCCOO⁻ is reported.     

Highly efficient and chemoselective cleavage of prenyl ethers using ZrCl4/NaBH4

An efficient and chemoselective deprotection of prenyl ethers of phenols and alcohols with ZrCl₄/NaBH₄ in DCM was achieved in high yields. The selectivity of prenyl ether deprotection is well demonstrated by carrying out the reaction in the presence of several other ether and ester functionalities.     

Mild and selective oxidation of alcohols to aldehydes and ketones using NaIO4/TEMPO/NaBr system under acidic conditions

A TEMPO-catalyzed selective oxidation of alcohols to the corresponding aldehydes and ketones using NaIO₄ as the terminal oxidant is reported. The NaIO₄/TEMPO/NaBr system provides a mild and efficient method for the oxidation of alcohols that are sensitive to basic conditions. Furthermore, the recoverable ionic liquid immobilized TEMPO-catalyzed oxidation of benzyl alcohol in ionic liquid-H₂O medium is also developed.     

A modified synthesis of tellurophene using NaBH4 to generate sodium telluride

A modified synthesis of tellurophene by reaction of diacetylene with sodium telluride is described. The primary modification involves the convenient in situ generation of sodium telluride by reduction of tellurium metal with NaBH₄ in water.     

[C4mim][PF6]和[C4mim][NTf2]离子液体辐射诱导的相行为及荧光行为变化

离子液体因其低挥发性, 高热稳定性及优良的萃取性能被认为是萃取分离放射性核素的新一代绿色溶剂, 而研究离子液体本身的辐射效应是其实际应用的重要前提. 本文以60Co为辐射源, 系统研究了γ辐照对两种常见的憎水性咪唑离子液体1-丁基-3-甲基咪唑六氟磷酸盐([C4mim][PF6])和1-丁基-3-甲基咪唑三氟甲基磺酰胺酸盐([C4mim][NTf2])的相行为及荧光行为的影响. 在相行为方面, γ辐照使离子液体的结晶驰豫时间增加, 导致其低温结晶延迟. 在荧光行为方面, γ辐照后离子液体的荧光光谱保持原有的“红边效应(red edge effect)”, 但随吸收剂量增加, 光谱整体发生红移(最大移动幅度达150 nm). 并且这种“红边效应”在辐照后离子液体的乙腈稀释剂中仍然存在, 且随稀释倍数增加光谱整体发生蓝移. [C4mim][PF6]和[C4mim][NTf2]离子液体辐照后的这种相行为及荧光行为的变化可归因于辐照对其阴阳离子空间相关性(缔合行为)的影响.     

Zn/[bmim]PF6-mediated Markovnikov allylation of unactivated terminal alkynes

A simple and highly regioselective method has been developed for the allylation of unactivated terminal alkynes with allyl bromide using Zn/[bmim]PF₆ as an inexpensive, readily available and recyclable reagent system. High conversions and enhanced selectivity together with the environmentally benign nature of the Zn/[bmim]PF₆ reagent system makes this method an attractive alternative to established methods.     

Facile reduction of malonate derivatives using NaBH4/Br2: an efficient route to 1,3-diols

Borane-dimethoxyethane generated from sodium borohydride-bromine mixtures efficiently reduces a wide range of malonate derivatives to the corresponding 1,3-diols. This new reagent system represents a milder alternative to current methods available, providing the requisite 1,3-diols in higher yields over shorter reaction times.     

Oxidation of aromatic aldehydes and ketones by H2O2/CH3ReO3 in ionic liquids: a catalytic efficient reaction to achieve dihydric phenols

A convenient and efficient application of hydrogen peroxide/methyltrioxorhenium in ionic liquids [bmim]BF₄ and [bmim]PF₆ for the oxidation of hydroxylated and methoxylated benzaldehydes and acetophenones to the corresponding phenols is described. Good yields of products were obtained in short reaction times.     

Ionic liquids/H2O systems for the reaction of epoxides with NaN3: a new protocol for the synthesis of 2-azidoalcohols

Oxiranes undergo ring opening rapidly with sodium azide in a [bmim]BF₄/H₂O or [bmim]PF₆/H₂O (2:1) solvent system, under mild and neutral reaction conditions to afford the corresponding 2-azidoalcohols in high to quantitative yields. The remarkable features of this procedure are improved yields, enhanced reaction rates, high regioselectivity and ease of recyclability of ionic liquids (ILs). The recovered ionic liquid can be reused for four to five times but with gradual decrease in activity.     

Fluorination of activated aromatic systems with Selectfluor™ F-TEDA-BF4 in ionic liquids

Selectfluor™ was shown to be soluble in ionic liquid, thus allowing the ‘green’ electrophilic fluorination of activated aromatic systems compounds in high chemoselectivity and yields.     

1,3-Cycloaddition of nitrones in ionic liquids catalyzed by Er(III): an easy access to isoxazolidines

1,3-Dipolar cycloadditions of nitrones with alkenes afforded the corresponding isoxazolidines in ionic liquids in the presence of Er(OTf)₃. The ionic liquid and the catalyst are recycled up to five times without any specific treatment or loss of activity. Extension of the procedure to the synthesis of isoxazolidinyl nucleosides has been investigated.     

Regioselective ring-opening reactions of 1,2-epoxides with thiols and arylselenols directly promoted by [Bmim]BF4

Regioselective ring-opening reactions of 1,2-epoxides with ArSH and ArSeH promoted by ionic liquid [Bmim]BF₄ were investigated. A variety of β-hydroxy selenides and β-hydroxy sulfides were obtained in excellent yields (81-99%) with good regioselectivities using a mild, simple and environmentally benign procedure.     

Bi(OTf)3/[bmim]BF4 as novel and reusable catalytic system for the synthesis of furan, pyrrole and thiophene derivatives

Bi(OTf)₃ immobilized in 1-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF₄ has been utilized for the first time as a novel and reusable catalytic system for the synthesis of heteroaromatics such as furan, pyrrole and thiophene derivatives from 1,4-diketones. This new procedure offers significant improvements in reaction rates and yields. The recovered ionic liquid containing bismuth triflate can be reused for subsequent runs with only a gradual decrease in activity.     

Enantioselective reduction of aliphatic ketones using NaBH4 and TarB-NO2, a chiral boronic ester

High enantioselectivities are obtained using a tartaric acid-derived boronic ester (TarB-NO₂) in combination with NaBH₄ for the asymmetric reduction of aliphatic ketones. The resulting alcohols are obtained in enantiomeric excesses ranging from 56% to 94%.     

Fluorolactonization of unsaturated carboxylic acids with F-TEDA-BF4 in ionic liquids

Fluorolactonization of unsaturated carboxylic acids under action of the electrophilic reagent F-TEDA-BF₄ in ionic liquids (ILs) has been studied. This reaction proceeds in ILs faster and provides a better stereoselectivity in comparison to acetonitrile as reaction media. Gem-difluorinated γ-lactones have been synthesized by interaction of unsaturated carboxylic acids with F-TEDA-BF₄ in ILs.