One-pot B(C6F5)3 catalyzed cascade synthesis of 2-substituted-2,3-dihydroquinazolin-4(1H)-ones

Abstract

A new and efficient B(C₆F₅)₃ catalyzed domino strategy has been developed for the synthesis of 2-substituted quinazolinones. The reaction utilizes 2-aminobenzamide and aldehydes for a one-pot protocol. A wide range of substrate scope, functional group tolerance, and operational simplicity with excellent yield are synthetically useful features.     

InCl3-catalyzed three-component reaction: a novel synthesis of dihydropyrano[3,2-b]chromenediones under solvent-free conditions

Three-component coupling (3CC) of kojic acid, aldehyde and 1,3-dione has been achieved in the presence of 10 mol % InCl₃ under solvent-free conditions to afford the corresponding dihydropyrano[3,2-b]chromenedione derivatives in good yields. This is the first example of the condensation of kojic acid, aldehyde and 1,3-diones to provide a novel series of kojic acid derivatives.     

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.     

Stoichiometric and Catalytic C−C and C−H Bond Formation with B(C6F5)3 via Cationic Intermediates

This work showcases a new catalytic cyclization reaction using a highly Lewis acidic borane with concomitant C−H or C−C bond formation. The activation of alkyne‐containing substrates with B(C₆F₅)₃ enabled the first catalytic intramolecular cyclizations of carboxylic acid substrates using this Lewis acid. In addition, intramolecular cyclizations of esters enable C−C bond formation as catalytic B(C₆F₅)₃ can be used to effect formal 1,5‐alkyl migrations from the ester functional groups to unsaturated carbon–carbon frameworks. This metal‐free method was used for the catalytic formation of complex dihydropyrones and isocoumarins in very good yields under relatively mild conditions with excellent atom efficiency.     

Adducts of (C6F5)3B with Selected Nitrogen

The Lewis acid (C₆F₅)₃B was reacted with ICN, NH₂CN, C₃N₃X₃ (X = H, Cl, F). The resulting Lewis acid base adducts ( 1—5 ) were fully characterized by analytic and spectroscopic methods. Additionally, the structures of the adducts 1—4 were determined by single crystal X‐ray analyses. It has been qualitatively shown, that a high field shift of the ¹¹B as well as the ¹⁹F NMR resonances of the o‐F atoms of the C₆F₅‐substituents suggests a longer B—N distance.     

Understanding the Influence of Donor-Acceptor Diazo Compounds on the Catalyst Efficiency of B(C6F5)3 Towards Carbene Formation

Diazo compounds have been largely used as carbene precursors for carbene transfer reactions in a variety of functionalization reactions. However, the ease of carbene generation from the corresponding diazo compounds depends upon the electron donating/withdrawing substituents either side of the diazo functionality. These groups strongly impact the ease of N₂ release. Recently, tris(pentafluorophenyl)borane [B(C₆F₅)₃] has been shown to be an alternative transition metal-free catalyst for carbene transfer reactions. Herein, a density functional theory (DFT) study on the generation of carbene species from α-aryl α-diazocarbonyl compounds using catalytic amounts of B(C₆F₅)₃ is reported. The significant finding is that the efficiency of the catalyst depends directly on the nature of the substituents on both the aryl ring and the carbonyl group of the substrate. In some cases, the boron catalyst has negligible effect on the ease of the carbene formation, while in other cases there is a dramatic reduction in the activation energy of the reaction. This direct dependence is not commonly observed in catalysis and this finding opens the way for intelligent design of this and other similar catalytic reactions.     

Methyl branching in polyethylene from homopolymerization of ethylene with N‐arylcyano‐β‐diketiminate methallyl nickel‐B(C6F5)3

N‐Arylcyano‐β‐diketiminate methallyl nickel complexes activated with B(C₆F₅)₃ were used in the polymerization of ethylene. The microstructure analysis of obtained polyethylene (PE) was done by differential scanning calorimetry and ¹³C nuclear magnetic resonance (NMR). The branched polymer structures produced by these catalysts were attributed to one step isomerization mechanism of the catalyst along the polymer chain. The ortho or para position of the cyano group with co‐ordinated B(C₆F₅)₃ in both methallyl nickel catalysts influenced the polymer molecular weight, branching, and consequently melting and crystallization temperatures. NMR spectroscopic studies showed predominantly the formation of methyl branches in the obtained PE. Catalysts under study gave linear low‐density PEs with good crystallinities at temperatures of reaction between 50 °C and 70 °C at moderate pressures (12.3 atm). A propylene–ethylene copolymer produced by the metallocene catalyst had the same concentration of branches as the PE synthesized from methallyl nickel/B(C₆F₅)₃. Comparing the two polyolefins with the same degree of branching, it was observed that the polymer obtained with the nickel catalyst proved to be twice more crystalline and had greater T_m. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 452–458     

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.     

新型B(C6F5)3/有机胺盐酸盐催化体系的反应研究

近年来, 受限路易斯酸碱对(FLPs: Frustrated Lewis Pairs)在小分子的活化以及在催化还原等方面所表现出的独特反应特性, 使得有关FLPs化学的研究受到了国内外广泛的关注. 设计了一种新型的FLPs催化体系, 该体系以三(五氟苯基)硼(BCF)为路易斯酸, 以多种不同取代的有机胺盐酸盐替代常规FLPs中的路易斯碱有机胺. 发现利用该体系与氢化硅烷反应, 不仅可以高产率地制备分离得到相应的伯、仲、叔硼氢化胺盐; 而且还可以这一体系作为催化剂, 以氢化硅烷作为还原剂, 在常温常压下可高选择性地部分或彻底还原大部分含羰基官能团醛酮等有机化合物. 由BCF/2,2,6,6-四甲基哌啶(TMP)盐酸盐组成的催化体系在对CO₂催化还原为甲烷的反应中, 亦较相应的BCF/TMP体系显示更高的活性. 还通过核磁共振详细地对比研究了原料有机胺盐酸盐、中间体氯代硼胺盐以及产物氢化硼胺盐中, 胺基氮上质子的核磁共振谱信息, 发现不仅胺基上取代基的位阻效应会影响到具有电四极矩性的¹⁴N磁性核的弛豫效应, 而且阴离子基团的配位强弱对胺基氮上质子的化学位移也会产生较大的影响.     

B(C6F5)3: an efficient catalyst for reductive alkylation of alkoxy benzenes and for synthesis of triarylmethanes using aldehydes

Tris(pentafluorophenyl)borane [B(C₆F₅)₃] has been used as an efficient catalyst for reductive alkylation of alkoxy benzenes using aldehydes as an alkylating agent in the presence of polymethylhydrosiloxane (PMHS). Various alkylated trimethoxybenzene derivatives have been prepared in good to high yields. In addition, B(C₆F₅)₃ was also used as a catalyst for the reaction of electron-rich arenes with aldehydes to obtain triarylmethanes. The use of reductive alkylation protocol for the synthesis of an isochroman and tetrahydroisoquinoline derivatives has also been demonstrated.     

Structures and Stability of Complexes of E(C6F5)3 (E = B,Al, Ga,In) with Acetonitrile

Complexes formed by interaction of E(C₆F₅)₃ (E = B, Al, Ga, In) with excess of acetonitrile (AN) were structurally characterized. Quantum chemical computations indicate that for Al(C₆F₅)₃ and In(C₆F₅)₃ the formation of a complex of 1:2 composition is more advantageous than for B(C₆F₅)₃ and Ga(C₆F₅)₃, in line with experimental observations. Formation of the solvate [Al(C₆F₅)₃ · 2AN] · AN is in agreement with predicted thermodynamic instability of [Al(C₆F₅)₃ · 3AN]. Tensimetry study of B(C₆F₅)₃ · CH₃CN reveals its stability in the solid state up to 197 °C. With the temperature increase, the complex undergoes irreversible thermal decomposition with pentafluorobenzene formation.     

CAN-catalyzed synthesis of 10-arylpyrano[3,2-b]chromene-4,9-diones under solvent-free conditions

A novel and efficient one-pot synthesis of 10-aryl-7,8-dihydropyrano[3,2-b]chromene-4,9(6H,10H)-diones by three-component reaction of aromatic aldehydes, 5-hydroxy-2-methylpyran-4-one, and cyclic 1,3-dicarbonyl compounds in the presence of a catalytic amount of ceric ammonium nitrate under solvent-free conditions is described. The advantages of this method include operational simplicity, short reaction time, recyclable catalyst, and high yields.     

One‐pot synthesis of 2‐amino‐4,8‐dihydropyrano[3,2‐b]pyranes and pyridopyrimidines under mild conditions

1,8‐Diazabicyclo[5.4.0]undec‐7‐ene immobilized on silica (SB‐DBU)Cl as a reusable and heterogeneous catalyst was applied for the one‐pot, three‐component synthesis of 2‐amino‐4,8‐dihydropyrano[3,2‐b]pyrane‐3‐carbonitriles and pyridopyrimidines, under solvent‐free conditions. The reaction was carried out at room temperature, and pure products were obtained in high yields and short reaction times (3–7 min). This work introduced an environmentally benign procedure for the synthesis of these classes of biological active compounds.     

Synthesis and Characterization of the 1 : 1-Adducts of In(C6F5)3 with Acetonitrile,Glyme, and DMAP (DMAP = 4-(N,N-dimethylamino)pyridine), and [PNP][In(C6F5)4] (PNP = bis(triphenylphosphinanyliden)immonium) – the Crystal Structure of [PNP][In(C6F5)4]

In(C₆F₅)₃ · CH₃CN and In(C₆F₅)₃ · glyme were synthesized from InCl₃ and Cd(C₆F₅)₂ in CH₃CN or glyme in 43% and 35% yield, respectively. Replacement of CH₃CN or (C₂H₅)₂O by DMAP yielded the corresponding 1 : 1-adduct. [PNP][In(C₆F₅)₄] was best prepared from the corresponding cesium salt which was best synthesized from the reaction of stoichiometric amounts of In(C₆F₅)₃ · CH₃CN, (CH₃)₃ SiC₆F₅ and CsF in good yield. [PNP][In(C₆F₅)₄] crystallizes in the triclinic space group P 1, a = 1104.9(4) pm, b = 1442.4(6) pm, c = 1833.8(8) pm, α = 110.87(2)°, β = 92.04(3)°, γ = 96.55(3)°, Z = 2.     

B(C6F5)3-Catalyzed E-Selective Isomerization of Alkenes

Herein, we report the B(C₆F₅)₃-catalyzed E-selective isomerization of alkenes. The transition-metal-free method is applicable across a diverse array of readily accessible substrates, giving access to a broad range of synthetically useful products containing versatile stereodefined internal alkenes. The reaction mechanism was investigated by using synthetic and computational methods.     

Pentafluorphenyliod(V)-Verbindungen. 2. Pentafluorphenyliodtetrafluorid C6F5IF4: Synthese durch Fluor-Aryl-Substitution an IF5 — Eigenschaften und Struktur. Strukturanalyse der monovalenten Iodstammverbindung C6F5I

Pentafluorophenyliodine(V) Compounds. 2. Pentafluorophenyliodine Tetrafluoride C₆F₅IF₄: Synthesis via Fluorine-Aryl-Substitution on IF₅ — Properties and Structure. Structural Analysis of the Monovalent Iodine Parent Compound C₆F₅I The nucleophilic fluorine-aryl substitution reaction on IF₅ with pentafluorophenyl, Bi(C₆F₅)₃, leads to C₆F₅IF₄ in good yields and high purity. The thermal stability of C₆F₅IF₄ and its NMR spectrometric behaviour in solution will be described. The crystal structure of C₆F₅IF₄ will be discussed in comparison to IF₅. In addition data of the molecular and crystal structure of the monovalent iodine parent compound C₆F₅I will be given.     

B(C6F5)3-catalyzed synthesis of benzylic azides

B(C₆F₅)₃ was found to catalyze the reaction between trimethylsilyl azide and benzylic acetates. Secondary and tertiary benzylic acetates were competent substrates in this reaction providing the azide products in moderate to high yields. Mechanistic experiments are consistent with the possible formation of a Lewis acid-base pair between the B(C₆F₅)₃ and trimethylsilyl azide.     

B(C6F5)3 catalyzed dehydrocarbon polycondensation of PhSiH3 with (MeO)4Si as model polyfunctional comonomers in new route to hydrophobic silicone TQ resins

Highly branched methoxy substituted phenylsilsesquioxane-silicate copolymers were obtained by dehydrocarbon polycondensation of phenylsilane (PhSiH₃) with tetramethoxysilane (TMOS) in toluene solution catalyzed by tris(pentafluorophenyl)borane [B(C₆F₅)₃]. This model reaction represents a new non-hydrolytic route to TQ silicone resins, which do not contain reactive and hydrophilic silanol groups and therefore, should be more stable and have better miscibility with some organic polymers. The soluble siloxane copolymers, which do not contain volatile oligomers, were obtained using the PhSiH₃:TMOS molar ratios below 0.9. The dehydrocarbon condensation is accompanied by metathetic exchange of hydrosilyl and methoxysilyl functions, which is responsible for the formation of links between units originating from the same comonomer. Competition between the dehydrocarbon condensation and metathesis is consistent with a mechanism involving the transient formation of a tertiary oxonium ion intermediate. ²⁹Si NMR analysis of the copolymer product proves that extensive cyclization occurs during the polycondensation, most likely leading to a significant proportion of ladder and cage like structures.     

Dioxygen Reactivity with a Ferrocene–Lewis Acid Pairing: Reduction to a Boron Peroxide in the Presence of Tris(pentafluorophenyl)borane

Ferrocenes, which are typically air‐stable outer‐sphere single‐electron transfer reagents, were found to react with dioxygen in the presence of B(C₆F₅)₃, a Lewis acid unreactive to O₂, to generate bis(borane) peroxide. Although several Group 13 peroxides have been reported, boron‐supported peroxides are rare, with no structurally characterized examples of the BO₂B moiety. The synthesis of a bis(borane)‐supported peroxide anion and its structural and electrochemical characterization are described.