Tris(pentafluorophenyl)borane catalyzed Ferrier azaglycosylation with sulfonamides and carbamates

The reaction of tri-O-acetyl-d-glucal with different nitrogen nucleophiles was effectively promoted by a catalytic amount of tris(pentafluorophenyl)borane for the first time in acetonitrile at room temperature to produce a variety of azapseudoglycals via Ferrier rearrangement in good yields and preferential anomeric selectivity.     

Aqueous cationic olefin polymerization using tris(pentafluorophenyl)gallium and aluminum

Tris(pentafluorophenyl)gallium ( 3 ) and aluminum ( 7 ) are active coinitiators for the production of medium‐high molecular weight (MW) polymers of styrene and isobutene (IB) under aqueous reaction conditions. Strong Brønsted acids formed in situ by reaction of these coinitiators with background moisture present in the monomer droplet ( 5 and 8 , respectively) are believed to be responsible for inducing cationic polymerization of these monomers. Of the two, 7 is the most active for IB polymerization in both aqueous media and anhydrous aliphatic solvents. These results are in contradistinction to tris(pentafluorophenyl)boron ( 2 ), which is incapable of polymerizing IB in aqueous or aliphatic media. The MWs of the polyisobutenes (PIBs) produced under aqueous conditions by either coinitiator greatly exceed those formed under similar reaction conditions by the strongly acidic chelating diborane (1,2‐C₆F₄[B(C₆F₅)₂]₂, 1 ) or diborole (1,2‐C₆F₄[9‐BC₁₂F₈]₂, 6 ). Both 3 and 7 are readily synthesized from the corresponding Group 13 halide compounds in conjunction with bis(pentafluorophenyl)zinc ( 4 ). Aqueous polymerization of IB dissolved in aliphatic solvents with 3 or 7 can yield PIBs with relatively narrow polydispersities. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Water-tolerant catalyst systems for the bulk cationic polymerization of para-methylstyrene and indene

Water-tolerant catalyst systems have been investigated for the cationic oligomerization of technical-grade p-methylstyrene and indene, for the production of industrially relevant aromatic resins. Systems based on 1-p-tolylethanol and 1-indanol (ROH) as initiators, in association with Cu(OTf)₂, Bi(OTf)₃ (OTf = triflate) and B(C₆F₅)₃ as co-initiators/catalysts, show interesting productivities at 60 °C under air, with as low as 0.2-1.0 mol% catalyst loading. Most of the reactions are not controlled in terms of molecular weights of the products, except for indene oligomerization by the borane catalyst where experimental M_n values match well the theoretical values, as determined by the amount of added initiator over a 5-fold range (with 2-10 mol% vs. monomer). The ROH/tris(pentafluorophenyl)borane system offers the best compromise in terms of productivity and control over the molecular weights of the oligomers, which can be manipulated by the amount of initiator and reaction temperature.     

Complexation of tris(pentafluorophenyl)silanes with neutral Lewis bases

A detailed analysis of monodentate and bidentate complexation of tris(pentafluorophenyl)silyl (TPFS) derivatives with neutral Lewis bases was performed. The NMR spectroscopy and X-ray diffraction analysis (11 structures) were the key methods to characterize tetra- or pentacoordinate silicon compounds, whereas the peculiarities of crystal packing were analyzed by means of DFT calculations. The interaction of TPFS-X (X = F, Cl, OTf) with strong Lewis bases (HMPA, N-methylpyrrolidinone) may afford three different species: neutral pentacoordinate TPFS(X)-L, cationic tetracoordinate TPFS-L⁺ X⁻, and cationic pentacoordinate TPFS-(L)⁺₂X⁻, representatives of each type were characterized by X-ray diffraction. A variety of complexes with bidentate complexation, featuring the trigonal bipyramidal geometry with apical C₆F₅-group was prepared and structurally characterized. The extent of Si-C_apical bond elongation depends on the donating ability of the coordinating ligand, with the longest Si-C bond of 1.981(1) Å observed for six-membered complex of TPFS-ether of N-(2-hydroxybenzoyl)pyrrolidine.     

A simple synthesis of B-2-(1-trimethylsilyl-1-alkyl)-1,3,2-dioxaborinanes. Isolation and selective oxidation to 1-trimethylsilyl-1-alkanols

(Z)-1-Trimethylsilyl-1-alkenes easily prepared by the hydroboration of the corresponding 1-trimethylsilyl-1-alkynes followed by protonolysis with acetic acid, readily react with dibromoborane-methyl sulfide complex in dichloromethane for 6 h. The resulting solution is then treated with 1,3-propane diol in a 1:1 mixture of dichloromethane and n-pentane at 0°C for half an hour to provide the corresponding gem-dimetalloalkanes containing boron and silicon. These alpha-trimethylsilylalkylboronate esters are purified by vacuum distillation in high yields (72-84%) and the structures of these novel intermediates are further confirmed by selective oxidation with alkaline hydrogen peroxide to provide the corresponding alcohols containing trimethylsilyl group.     

Facile hydroboration of (Z)-1-trimethylsilyl-1-alkenes with dichloroborane-dioxane complex: An easy access to gem-dimetalloalkanes containing boron and silicon

(Z)-1-trimethylsilyl-1-alkenes easily prepared by the hydroboration of the corresponding 1-trimethylsilyl-1-alkynes followed by protonolysis with acetic acid, readily react with dichloroborane-dioxane complex in dichloromethane for 6 h. The resulting solution is then treated with 1,3-propane diol in dichloromethane at 0 °C for half an hour to provide the corresponding gem-dimetalloalkanes containing boron and silicon. These α-trimethylsilylalkylboronate esters are purified by vacuum distillation in high yields (72-84%) and the structures of these novel intermediates are further confirmed by selective oxidation with alkaline hydrogen peroxide to provide the corresponding alcohols containing α-trimethylsilyl group in 78-88% isolated yields.     

Chiral terpene auxiliaries. Part 1: Highly enantioselective reduction of ketones with borane catalyzed by an oxazaborolidine derived from (−)-β-pinene

(1R,2S,3R,5R)-3-Amino-6,6-dimethyl-2-hydroxybicyclo[3.1.1]heptane was synthesized in three steps from (−)-β-pinene. It was used for the in situ generation of a B-methoxy-oxazaborolidine catalyst for the asymmetric reduction of alkyl-aryl ketones with borane-dimethyl sulfide complex. In the presence of 3 mol % of the catalyst, the product alcohols were obtained in high yields and with enantiomeric excesses in the range of 93-98%.     

Formation of a new ring system: Tetrazolo[5,1-f][1,2]azaborinin

Phenothiazinyldienes obtained from tetrazolopyridinium salts and phenothiazine derivatives were subjected to reduction by borane-dimethyl sulfide in THF. Structure elucidation of the products revealed that one of the olefinic bond underwent reduction and, furthermore, borane addition at the double bond took place to yield derivatives of tetrazolo[5,1-f][1,2]azaborinin as a new fused ring system involving a bridge-head nitrogen atom. The new products have been synthesized and characterized by X-ray analysis, solution and solid-state NMR.     

三(五氟苯基)硼烷掺杂有机/高分子半导体的研究进展

有机/高分子共轭聚合物的结构设计是制备高性能有机半导体的有效策略,但该过程存在着设计合成周期长、制备步骤复杂和产率偏低等问题。为了克服这些问题,近年来人们越来越关注对有机/高分子半导体的掺杂。然而,传统电荷转移掺杂剂(如卤族单质I₂、金属氧化物Fe₃O₄、小分子F4TCNQ等)存在掺杂效率低、溶解度差和掺杂条件苛刻等问题。相比之下,三(五氟苯基)硼烷具有溶解度高、掺杂效率高、广泛适应性等优点。本文结合相关文献综述了三(五氟苯基)硼烷掺杂有机半导体的物理机制,并探讨了掺杂有机半导体的性质;此外,还总结了三(五氟苯基)硼烷掺杂在不同光电功能器件中的应用并明确了今后的研究方向。     

Unexpected Reduction of Indole Double Bond in Mitragynine Using n-Butylsilane and Catalytic Tris(pentaflorophenyl)borane

An unexpected reduction of indolic double bond of mitragynine was described by using n-butyl silane and tris(pentafluorophenyl)triborane.     

选择性反应及其合成应用的研究--Ⅰ.高度区域及立体选择性硼氢化和1,2:5,6一二一(0-亚异丙基)-α-D-半乳-呋喃糖合成方法的改进

由D—葡萄糖(Ⅰ),经四步反应可得标题化合物(Ⅴ)。为了在较短的时间内制得足够量的纯净的3—脱氧1,2:5,6—二(O—亚异丙基)—α—D—赤—己—3—烯呋喃糖(Ⅳ),可将3—O—对甲苯磺酰基—1,2:5,6—二—(O—亚异丙基)—α—D—葡—呋喃糖(Ⅲ)和粉状氢氧化钾置于Kugelrohr装置中进行反应。仔细控制反应条件,化合物(Ⅳ)的产率达到72％。在硼烷—甲硫醚配合物(H_3B:SMe_2)与烯(Ⅳ)起硼氢化反应后,用碱性过氧化氢处理,可得产物(Ⅴ),产率76—81％。此硼氢化反应具有高度区域选择性和立体选择性。     

Pentafluorphenyliod(III)-Verbindungen. 2. Fluor-Aryl Substitution an Iodtrifluorid: Synthese von Pentafluorphenylioddifluorid C6F5IF2 und Bis(pentafluorphenyl)iodonium Pentafluorphenylfluoroboraten [(C6F5)2I]+[(C6F5)nBF4−n]−

Pentafluorophenyliodine(III) Compounds. 2. Fluorine-Aryl Substitution Reactions on Iodinetrifluoride: Synthesis of Pentafluorophenyliodinedifluoride C₆F₅IF₂ and Bis(pentafluorophenyl)iodonium Pentafluorophenylfluoroborates[(C₆F₅)₂I]⁺[(C₆F₅)_nBF_4?n]^? Mono- and disubstitution can be achieved in the fluorine-aryl substitution reaction on the low-temperature phase IF₃ in CH₂Cl₂ at ?78°C depending on the aryl transfer reagent. With B(C₆F₅)₃ [(C₆F₅)₂I]⁺ [(C₆F₅)_nBF_4?n]^? (68% yield) and with Cd(C₆F₅)₂ C₆F₅IF₂ (97% yield) is obtained whereas with C₆F₅SiMe₃ no fluorine-aryl substitution takes place on IF₃ even under basic conditions (EtCN or F^? addition). At ?78°C in EtCN solution IF₃ does not disproportionate but attacks the solvent under formation of HF.     

1,1,3,3,3-Pentafluoro-2-pentafluorophenyl-1,2-epoxypropane and trimethylphosphite: unusual 1,4-dioxan-2,5-dione ring formation

1,1,3,3,3-Pentafluoro-2-pentafluorophenyl-1,2-epoxypropane 1 reacted with trimethylphosphite giving two diastereomers, (Z)- and (E)-3,6-bis(trifluoromethyl)-3,6-bis(pentafluorophenyl)-1,4-dioxan-2,5-dione 2a, b in a 1:1 ratio, cyclodimerisation product of the intermediately generated α-lactone 4. Compounds 2a, b were hydrolysed to furnish 3,3,3-trifluoro-2-hydroxy-2-(2,3,4,5,6-pentafluorophenyl)propionic acid 5.     

Tris(pentafluorophenyl)borane: a mild and efficient catalyst for the chemoselective tritylation of alcohols

An efficient acid-catalyzed protection of alcohols as trityl ethers is described using triphenylmethanol in the presence of tris(pentafluorophenyl)borane (3 mol %) in dichloromethane at room temperature. The chemoselectivity of this protocol is demonstrated by studying the tritylation of a primary alcohol in the presence of a secondary alcohol and also the mildness of this catalyst was studied with substrates containing acid labile protecting groups.     

Effects of tris(pentafluorophenyl)borane on the activation of the Ni(II)-based catalyst in the addition polymerization of norbornene

The activity of the transition metal complex, such as Ni(2-ethyl hexanoate)₂ (1), Co(2-ethyl hexanoate)₂ (2), TiCl₄ (3), or CpTiCl₃ (4) (Cp = cyclopentadiene), in combination with MAO (methylaluminoxane), was investigated in the polymerization of norbornene. The Ni(II) complex 1 with MAO showed moderate activity to give 20.8 kg_polymer/mol_Ni h, while the other three complexes 2-4 with MAO just showed trivial activity. Effects of the Lewis acids on the activation of the catalyst of 1/MAO were examined. The employment of B(C₆F₅)₃ with 1/MAO significantly enhanced the activity to give up to around 133 kg_polymer/mol_Ni h. The use of other borane compounds, such as B(C₆H₅)₃ and BEt₃, or the stronger electron acceptor BF₃ · OBu₂, with 1/MAO in place of B(C₆F₅)₃ clearly showed the main functions of B(C₆F₅)₃. The high Lewis acidity of B(C₆F₅)₃ enabled it to develop matured active complexes, thus enhancing the activity. Several Ni(II) complexes were employed to determine whether their activity was comparable to that of complex 1 in norbornene polymerization. The study of the ¹H and ¹³C NMR spectra of the polynorbornene produced with 1/B(C₆F₅)₃/MAO showed that the initiation of addition polymerization occurred through the insertion of the exo face of the norbornene into the active complex. Effects of the variation in the polymerization variables, such as the levels of B(C₆F₅)₃ and MAO, temperature, and solvent, on the polymerization were discussed.     

Tris(pentafluorophenyl)borane catalyzed acylation of alcohols,phenols, amines,and thiophenols under solvent-free condition

The acylation of alcohols, phenols, amines, and thiophenols was accomplished with 0.5 mol % of tris(pentafluorophenyl)borane [B(C₆F₅)₃] at ambient temperature under solvent-free condition. Major advantages of this method include high yield, short reaction time, simple procedure, compatibility with sensitive protecting groups as well as other functional groups, absence of racemization of optical active compounds, and epimerization of sugars.     

Triarylborane‐Catalyzed Alkenylation Reactions of Aryl Esters with Diazo Compounds

Herein we report a facile, mild reaction protocol to form carbon–carbon bonds in the absence of transition metal catalysts. We demonstrate the metal‐free alkenylation reactions of aryl esters with α‐diazoesters to give highly functionalized enyne products. Catalytic amounts of tris(pentafluorophenyl)borane (10–20 mol %) are employed to afford the C=C coupled products (31 examples) in good to excellent yields (36–87 %). DFT studies were used to elucidate the mechanism for this alkenylation reaction.     

Synthesis and structural characterization of carbon-centered tris(pentafluorophenyl)silyl derivatives

A general method for the synthesis of carbon-centered tris(pentafluorophenyl)silyl derivatives (RSi(C₆F₅)₃) by reaction of trichlorosilanes (RSiCl₃) with pentafluorophenylmagnesium bromide was described. The crystal structures of obtained compounds were studied by X-ray diffraction analysis (7 structures). The peculiarities of crystal packing were analyzed by means of DFT calculations.     

A dichotomy in the enantioselective oxidation of aryl benzyl sulfides: A combined experimental and computational work

Pentafluorobenzyl pentafluorophenyl sulfide is oxidised with moderate e.e. value and a low yield by the usually highly successful oxidation protocol based upon tert-butyl hydroperoxide (TBHP) in the presence of a titanium/hydrobenzoin complex. This disappointing result resisted until the present work, in which the switch of the oxidation agent (from TBHP to cumene hydroperoxide), suggested by our previous computations, yielded the enantiopure sulfoxide. This valuable chiral compound was obtained in good yields (76%) without resorting to a chromatographic separation. DFT computations uncovered that this favourable reactivity was originated by a stabilizing π?π?stacking between the phenyl group of the oxidant and the pentafluorophenyl moiety of the substrate.     

Acid-catalyzed N-alkylation of tosylhydrazones using benzylic alcohols

N-Alkylation of tosylhydrazones in the presence of an acid catalyst is described for the first time. Tris(pentafluorophenyl) borane was found to be a mild and efficient catalyst when benzylic alcohols were used as the alkylating agents.