Copper-catalyzed remote CH ethoxycarbonyldifluoromethylation of 8-aminoquinolines with bis(pinacolato)diboron as reductant

A simple protocol for the copper/B₂pin₂-catalyzed CH ethoxycarbonyldifluoromethylation of 8-aminoquinoline scaffolds with functionalized difluoromethyl bromides and iodines was developed, affording the desired products in moderate to good yields. This reaction was carried out under mild conditions and features good substrate tolerance.     

氮杂环卡宾氯化亚铜催化对称内炔烃硼氢化反应

本文报道了惰性对称内炔烃硼氢化反应,高效合成系列硼酸酯化合物。以氮杂环卡宾氯化亚铜催化联硼酸频哪醇酯与对称内炔烃发生反应,生成烯基铜试剂,再经甲醇质子化,高效合成了构型单一的顺式烯基硼酸酯,产物经~1H NMR、~(13)C NMR、HRMS表征。系统考察了反应各项参数,讨论了反应可能的历程。本研究的炔烃硼氢化方法简便高效,催化剂稳定,无需使用膦配体,环境友好。     

Palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with vinyl triflates β-substituted by a carbonyl group: efficient synthesis of β-boryl-α,β-unsaturated carbonyl compounds and their synthetic utility

Cross-coupling reaction of bis(pinacolato)diboron with β-(trifluoromethanesulfonyloxy)-α,β-unsaturated carbonyl compounds was carried out in the presence of PdCl₂(PPh₃)₂-2PPh₃ (3 mol%) and KOPh in toluene or K₂CO₃ in dioxane for the synthesis of cyclic and acyclic β-boryl-α,β-unsaturated esters, amides, and ketones in high yields. The vinylboronates thus obtained readily participated in carboncarbon bond formation such as cross-coupling with vinyl triflates and 1,4-addition to α,β-unsaturated ketones.     

A mild copper catalyzed method for the selective deprotection of aryl allyl ethers

Copper boryl reagents enable the selective cleavage of aryl allyl ethers to the corresponding phenols in good to moderate yields.     

Copper-catalyzed synthesis of gem-difluoroallylboronates from α-trifluoromethyl alkenes and B2pin2

A novel and efficient method for the synthesis of gem-difluoroallylboronates via copper-catalyzed defluorinative borylation of α-trifluoromethyl alkenes with B₂pin₂ using Xantphos as ligand and NaOtBu as base was developed.     

Cyclopalladated ferrocenylimine: a highly effective catalyst for the borylation/suzuki coupling reaction

The cyclopalladated ferrocenylimine was an efficient catalyst for the borylation/Suzuki coupling reaction. The catalytic loading for the reaction containing bromoarenes was 1 mol %. When iodobenzene was used, the catalytic loading was as low as 0.1 mol %. Furthermore, the cyclopalladated ferrocenylimine also exhibited excellent catalytic power in the case of substrates containing electron-donating substituents, with yields reaching 93% or higher.     

An improved procedure for the synthesis of arylboronates by palladium‐catalyzed coupling reaction of aryl halides and bis(pinacolato)diboron in polyethylene glycol

A new protocol has been developed for the synthesis of arylboronates by a coupling reaction of aryl halides and bis(pinacolato)diboron using bis(triphenylphosphine)palladium dichloride/sodium acetate/polyethylene glycol 600 [Pd(PPh₃)₂Cl₂/NaOAc/PEG 600] as an efficient catalytic system. Copyright © 2011 John Wiley & Sons, Ltd.     

Transition metal-catalyzed borylation of alkanes and arenes via C---H activation

Since 1999, direct borylation of hydrocarbons catalyzed by a transition metal complex has been extensively studied by several groups and has become an economical, efficient, elegant, and environmentally benign protocol for the synthesis of a variety of organoboron compounds. Re-, Rh-, Ir- and Pd-catalyzed C---H borylation of alkanes, arenes and benzylic positions of alkylarenes by bis(pinacolato)diboron or pinacolborane provide alkyl-, aryl-, heteroaryl- and benzylboron compounds, respectively. In this review, seminal early works and exciting recent developments in the area of direct borylation of hydrocarbons via C---H activation are summarized.     

Generation of bis(pentafluorophenyl)borane-dimethyl sulfide complex as a solution of hexane and its application to hydroboration of alk-1-yne with pinacolborane

A solution of bis(pentafluorophenyl)borane-dimethyl sulfide complex in hexane was generated by redistribution between tris(pentafluorophenyl)borane and borane-dimethyl sulfide complex. In the resulting solution a stoichiometric hydroboration of alk-1-yne with pinacolborane proceeded well at room temperature to afford (E)-alk-1-enylboronic acid pinacol ester in high yield. Bis(pentafluorophenyl)borane-dimethyl sulfide complex served as a mediator for the hydroboration.     

Copper-Catalyzed Diboron-Mediated cis-Semi-Hydrogenation of Alkynes under Facile Conditions

Cis-alkenes are ubiquitous in biological molecules, which makes it greatly significant to develop efficient methods toward construction of cis-olefins. Herein, we reported a facile semi-hydrogenation of alkynes to cis-alkenes in an efficient way with cuprous bromide/tributylphosphine as the catalyst and bis(pinacolato)diboron/methanol as the hydrogen donor. The method features convenient and facile reaction conditions, wide substrate scope, high yields, and high stereoselectivity.     

Chiral organochlorosilanes derived from terpenes: diastereoselective hydrosilylation of methylene bicyclo[2.2.1]heptanes with HSiMenCln − 2 (n=0-2)

The H₂PtCl₆ catalysed hydrosilylation of the terpenes (+)-α-fenchene (XI), (−)-2-methylene bornane (XII), (+)-camphene (XIII) and (−)-3-methylene fenchane (XIV) using HSiMe₂Cl or HSiMeCl₂ proceeds with high regioselectively and in some cases, with high diastereoselectivity. KF-assisted oxidation of the hydrosilylation products gives predominately endo-terpene alcohols. The alcohols have inverted endo/exo ratios to those formed by oxidative hydroboration. Reaction of XIV with HSiMe₂Cl or HSiMeCl₂ is accompanied by a clean rearrangement of the isocamphane skeleton into (+)-2-methylene bornane (XII) prior to hydrosilylation.     

A mild and general method for the synthesis of 2-substituted-5-hydroxypyrimidines

5-Bromopyrimidines are converted to 5-hydroxypyrimidines using a mild synthetic procedure. The method is general and can be applied to compounds containing functional groups which are not compatible with the other reagents previously available for this conversion.     

Ruthenium-catalyzed selective hydrosilylation reaction of allyl-functionalized PEG derivatives

Reactions of allyl-functionalized poly(ethylene glycol) (PEG) derivatives with alkoxysilanes proceeded efficiently to furnish the corresponding hydrosilylated products in good to excellent yields using a ruthenium catalyst, [RuCl₂(nbd)]_n. A preliminary mechanistic study supported the pivotal role of the PEG moiety, which coordinated to the ruthenium atom during the reaction to achieve high reaction selectivity. This method may be applicable to the synthesis of various PEGs with a silyl terminus, which is useful as biocompatible and low toxic silane coupling agents.     

The catalytic activity of alkali metal alkoxides and titanium alkoxides in the hydrosilylation of unfunctionalized olefins

The catalytic activities of titanium alkoxides and alkali metal alkoxides for hydrosilylation of unfunctionalized olefins have been studied. Titanium(IV) alkoxides showed excellent catalytic activity, while alkali metal alkoxides have low catalytic activity for the hydrosilylation of olefins. However, by using titanocene dichloride as an additive, alkali metal alkoxides showed also excellent catalytic property for hydrosilylation. In comparison with titanium alkoxides, no α-adduct was obtained by using alkali metal alkoxides/Cp₂TiCl₂ as catalysts.     

One-pot synthesis of polyimides via Ni-catalyzed coupling of bis(chlorophthalimide)s

A one-pot synthesis method for the preparation of polyimides containing biphenyl units was developed via nickel-catalyzed coupling reaction of bis(chlorophthalimide)s which were prepared from chlorophthalic anhydrides and diamines in xylene. The resulting polyimides had inherent viscosities of above 0.60 dL g⁻¹. In the meantime, the copolymerizations from a mixture of three isomeric bis(chlorophthalimide)s gave the polymers with inherent viscosities of 0.36-0.55 g dL⁻¹. The solubility and film formability of the copolymers were better than those of homopolymers from bis(4-chlorophthalimide). The 10% weight loss of these polyimides was between 470 and 531 °C.     

Tri(t-butyl)phosphine-assisted selective hydrosilylation of terminal alkynes

<正>A highly efficient and regio-/stereoselective method of hydrosilylating terminal alkynes was developed using Pt(DVDS)-tri(t-butyl) phosphine catalyst system at room temperature.Trans-products or alpha-products were obtained almost exclusively depending on the alkynes and silanes employed.     

A novel fumed silica-supported nitrogenous platinum complex as a highly efficient catalyst for the hydrosilylation of olefins with triethoxysilane

A novel fumed silica-supported nitrogenous platinum complex was conveniently prepared from cheap γ-aminopropyltriethoxysilane via immobilization on fumed silica in toluene, followed by a reaction with hexachloroplatinic acid. The title complex was characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It was found that the complex is an efficient and stable catalyst for the hydrosilylation of olefins with triethoxysilane. The title platinum complex could be separated by simple filtration and reused several times without any appreciable loss in the catalytic activity.     

Bridge functionalized bis-N-heterocyclic carbene rhodium(I) complexes and their application in catalytic hydrosilylation

A series of chelating bridge functionalized bis-N-heterocyclic carbenes (NHC) complexes of rhodium (I) were prepared by reacting the corresponding imidazolium salts with [Rh(COD)Cl]₂ in an in-situ reaction. For the N-methyl substituted complex with a PF₆-anion an X-ray crystal structure was exemplary obtained. All complexes were spectroscopically characterized and tested for the hydrosilylation of acetophenone.     

Titanium-catalyzed hydrosilylation of olefins: A comparison study on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4 catalyst system

Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/Sm (Cp?=?cyclopentadienyl) under solvent free conditions have been investigated. By using Cp₂TiCl₂/Sm as catalyst system, β-adducts and hydrogenation products were detected. Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/LiAlH₄ under room temperature has also been studied. The influence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) on Cp₂TiCl₂/Sm and Cp₂TiCl₂/LiAlH₄, respectively, indicated that hydrosilylation of olefins catalyzed with Cp₂TiCl₂/Sm went through a free radical reaction pathway while a coordination mechanism was applied for Cp₂TiCl₂/LiAlH₄ catalyst system.     

Copper-catalyzed asymmetric hydrosilylation of ketones using air and moisture stable precatalyst Cu(OAc)2·H2O

Air and moisture stable copper(II) salts can be used to catalyze the hydrosilylation of aromatic ketones. The combination of catalytic amounts of copper(II) acetate or copper(II) acetate monohydrate (Cu(OAc)₂·H₂O) and BINAP in the presence of organosilanes as the stoichiometric reducing agent generates an active catalyst for the reduction of ketones.