Highly Efficient Method for Synthesis of Bis(Indolyl)Methanes Catalyzed by FeCl3−based Ionic Liquid

A simple and highly efficient green protocol for synthesis of bis(indolyl)methanes was carried out by the reaction of indole with aldehydes and ketones in the presence of FeCl_3?based ionic liquid. These liquids serve as efficient media as well as Lewis acid catalysts.     

Reactions of a Ga/P‐Based Frustrated Lewis Pair with HX (X = F – I), Heterocumulenes R–NCY (Y = O,S) and Chalcogens–Adduct Formation and Surprising Stability towards Protolysis

Treatment of the geminal Ga/P‐based frustrated Lewis pair (FLP) Mes₂P–C(GatBu₂)=C(H)–Ph ( 1 ) with HX (X = F, Cl, Br, I) afforded the corresponding adducts 2 with the protons bound to the P and the halide anions coordinated to the Ga atoms. Short intramolecular contacts may indicate P–H ··· X hydrogen bonding interactions. The Br and I compounds ( 2c , 2d ) were accessible in moderate yields even when aqueous solutions of the acids were employed. These unexpected reactions confirm the surprising stability of FLP 1 towards protolysis. Heterocumulenes R–N=C=Y (Y = O, S) and 1 yielded adducts with two different structural motifs. The N=C=Y groups were coordinated to the FLP either via the C=Y (Y = S; Ph–N=C=O) or the C=N bonds (Ph–N=C=O, Et–N=C=O). For phenyl isocyanate the C=O bonded isomer was observed in the solid state, while both isomeric forms were detected in solution. Steric shielding and the hardness of the atoms may influence the formation of the respective isomer. Cleavage of the C=S bonds of isothiocyanates was observed for the first time and afforded a sulfur adduct 9a , in which an S atom (electron sextet) was bound to the lone pair of electrons at phosphorus and to the Lewis acidic Ga atom. Four‐membered PCGaY heterocycles resulted, which were also synthesized in high yields by the direct reaction of 1 with propylene sulfide or selenium.     

离子交联聚氯乙烯的结构与性能

由氯乙烯/丙烯酸悬浮共聚合成了不同羧基含量的PVC树脂,采用溶液反应和熔融加工法制备离子交联PVC,对其结构和性能进行了研究.结果表明,共聚物中羧基主要以二聚体形式存在,用金属离子中和能形成部分络合结构;用Ca²⁺、Mg²⁺离子络合的羧基含量较高的VC/AA共聚物存在离子对聚集态结构;离子对含量、金属离子种类和增塑剂浓度影响离子聚集相的比例和稳定性,离子聚集具有热可逆性;离子交联使PVC的T_g、熔体粘度和回弹性提高.     

Nitrimines as Reagents for Metal‐Free Formal C(sp2)–C(sp2) Cross‐Coupling Reactions

Nitrimines are employed as powerful reagents for metal‐free formal C(sp²)–C(sp²) cross‐coupling reactions. The new chemical process is tolerant of a wide array of nitrimine and heterocyclic coupling partners giving rise to the corresponding di‐ or trisubstituted alkenes, typically in high yield and with high stereoselectivity. This method is ideal for the metal‐free construction of heterocycle‐containing drug targets, such as phenprocoumon.     

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.     

Catalysis by Platinum(II) Iodo Complexes of C(sp2)–C(sp2) Electrophile Coupling

Kinetics and Catalysis - The catalytic C(sp2)–C(sp2) coupling of vinyl iodide was performed to form 1,3-butadiene in the PtII–NaI–С2Н3I–acetone-D6 system at...     

One-pot Synthesis of Lewis Acidic Ionic Liquids for Friedel-Crafts Alkylation

Lewis acidic ionic liquids have been receiving extensive interest as green substitute for H2SO4, HF and AlCl3 catalysts in chemical processes1. In view of the principles of green chemistry2, ionic liquids themselves are highly expected to be obtained via …     

B(C6F5)3-catalyzed metal-free hydrogenations of 2-quinolinecarboxylates

A metal-free hydrogenation of 2-quinolinecarboxylates has been realized by using 5?mol% of B(C₆F₅)₃ as catalyst. A variety of tetrahydroquinolines were obtained in 57–99% yields. An attempt for the asymmetric hydrogenation with chiral boron Lewis acids generated from chiral dienes afforded very low ee’s.     

Rational Design of a Palladium-Catalyzed C(sp) -C(sp) Cross-Coupling Reaction Inspired by Kinetic Studies

Less is More: A highly selective Pd-catalyzed C(sp) -C(sp) cross-coupling reaction between terminal alkynes and 1-bromoacetylenes has been developed. Catalyst loading is low (only 0.0001-0.01?mol?% of Pd is required) and provides products with high selectivities and good to excellent yields under mild conditions. TBAB=tetrabutylammonium bromide, TON=turnover number.     

Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp2)–C(sp3)Coupling Reactions

A number of new transition metal catalyzed methods for the formation of C(sp²)–C(sp³) bonds have recently been described. These reactions often utilize bidentate polypyridyl‐ligated Ni catalysts, and paramagnetic Ni^I halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl‐ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp²)–C(sp³) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp²)–C(sp³) coupling through stoichiometric studies and also explore their catalytic activity.     

Highly stable magnetically separable copper nanocatalyst as an efficient catalyst for C(sp2)–C(sp) and C(sp2)–C(sp2) cross‐coupling reactions

A copper catalyst has been explored as an efficient and recyclable catalyst to effect Sonogashira and Suzuki cross‐coupling reactions. After modification of 2‐(((piperazin‐1‐ylmethyl)imino)methyl)phenol (PP) on the surface of amorphous silica‐coated iron oxide (Fe₃O₄@SiO₂@Cl) magnetic core–shell nanocomposite, copper(II) chloride was employed to synthesize the Fe₃O₄@SiO₂@PP‐Cu catalyst, affording a copper loading of 1.52 mmol g⁻¹. High yield, low reaction times, non‐toxicity and recyclability of the catalyst are the main merits of this protocol. The catalyst was characterized using Fourier transform infrared, X‐ray photoelectron, energy‐dispersive X‐ray and inductively coupled plasma optical emission spectroscopies, X‐ray diffraction, scanning and transmission electron microscopies, and vibrating sample magnetometry.     

Asymmetric Organocatalytic Direct C(sp2)H/C(sp3)H Oxidative Cross‐Coupling by Chiral Iodine Reagents

An asymmetric organocatalytic direct C? H/C? H oxidative coupling reaction of N¹,N³‐diphenylmalonamides has been well established by using chiral organoiodine compounds as catalysts, wherein four C? H bonds were stereoselectively functionalized to give structurally diverse spirooxindoles with high levels of enantioselectivity. More importantly, the findings indicated that chiral hypervalent organoiodine reagents can serve as alternative catalysts for the creation of enantioselective functionalization of inactive C? H bonds.     

Reaction of a 6-dimethylaminopentafulvene with the Mes2PCH2CH2B(C6F5)2 frustrated Lewis pair

The frustrated Lewis pair Mes(2)PCH(2)CH(2)B(C(6)F(5))(2) reacts readily with 6-dimethylamino-6-methylfulvene at room temperature to yield the trans-1-[B(C(6)F(5))(2)]-2-[CH(2)CH(2)PMes(2)] disubstituted fulvene derivative 9 that features an internal N-B contact. Thermolysis (80 °C in toluene) results in a complete isomerization to the respective 1-[B(C(6)F(5))(2)]-3-[CH(2)CH(2)PMes(2)] isomer 10. Both compounds were characterized by using X-ray diffraction. A reaction scheme is formulated to rationalize the specific formation of these compounds, involving a retro-hydroboration/hydroboration sequence. The reaction of the 6-dimethylaminofulvene with HB(C(6)F(5))(2) yielded the corresponding parent compound 13 that was also characterized by X-ray diffraction.     

Decarboxylative C(sp3)−O Cross‐Coupling

Alkyl aryl ethers are an important class of compounds in medicinal and agricultural chemistry. Catalytic C(sp³)?O cross‐coupling of alkyl electrophiles with phenols is an unexplored disconnection strategy to the synthesis of alkyl aryl ethers, with the potential to overcome some of the major limitations of existing methods such as C(sp²)?O cross‐coupling and S_N2 reactions. Reported here is a tandem photoredox and copper catalysis to achieve decarboxylative C(sp³)?O coupling of alkyl N‐hydroxyphthalimide (NHPI) esters with phenols under mild reaction conditions. This method was used to synthesize a diverse set of alkyl aryl ethers using readily available alkyl carboxylic acids, including many natural products and drug molecules. Complementarity in scope and functional‐group tolerance to existing methods was demonstrated.     

Rollover‐Assisted C(sp2)C(sp3) Bond Formation

Rollover cyclometalation involves bidentate heterocyclic donors, unusually acting as cyclometalated ligands. The resulting products, possessing a free donor atom, react differently from the classical cyclometalated complexes. Taking advantage of a “rollover”/“retro‐rollover” reaction sequence, a succession of oxidative addition and reductive elimination in a series of platinum(II) complexes [Pt(N,C)(Me)(PR₃)] resulted in a rare C(sp²)?C(sp³) bond formation to give the bidentate nitrogen ligands 3‐methyl‐2,2′‐bipyridine, 3,6‐dimethyl‐2,2′‐bipyridine, and 3‐methyl‐2‐(2′‐pyridyl)‐quinoline, which were isolated and characterized. The nature of the phosphane PR₃ is essential to the outcome of the reaction. This route constitutes a new method for the activation and functionalization of C?H bond in the C(3) position of bidentate heterocyclic compounds, a position usually difficult to functionalize.     

Stereospecific Pd‐Catalyzed Intermolecular C(sp3)–C(sp) Cross‐Coupling of Diarylmethyl Carbonates and Terminal Alkynes Under Base‐Free Conditions

A palladium‐catalyzed intermolecular decarboxylative C(sp³)–C(sp) coupling of diarylmethyl carbonates and terminal alkynes has been developed. The reaction proceeds smoothly under external base‐free conditions to deliver the corresponding alkynylated diarylmethanes with the liberation of CO₂ and MeOH as the sole byproducts. Moreover, enantioenriched diarylmethyl carbonates are stereospecifically converted to optically active cross‐coupling products with inversion of configuration. Thus, the stereospecific palladium catalysis can provide new and unique access to the alkynylated chiral tertiary stereocenters, which are relatively difficult to construct by conventional methods.     

Cobalt‐Catalyzed Intermolecular C(sp2)O Cross‐Coupling

Cobalt(II)‐catalyzed C(sp²)?O cross‐coupling between aryl/heteroaryl alcohols and vinyl/aryl halides in the presence of Cu^I has been achieved under ligand‐free conditions. In this reaction, copper plays a significant role in transmetalation rather than being directly involved in the C?O coupling. This unique Co/Cu‐dual catalyst system provides an easy access to a library of aryl–vinyl, heteroaryl–styryl, aryl–aryl, and heteroaryl–heteroaryl ethers in the absence of any ligand or additive.     

Direct C(sp2)C(sp3) Cross‐Coupling of Diaryl Zinc Reagents with Benzylic,Primary, Secondary,and Tertiary Alkyl Halides

The direct C(sp²)? C(sp³) cross‐coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides proceeded in the absence of coordinating ethereal solvents at ambient temperature without the addition of a catalyst. The C(sp²)? C(sp³) cross‐coupling showed excellent functional‐group tolerance, and products were isolated in high yields, generally without the requirement for purification by chromatography. This process represents an expedient, operationally simple method for the construction of new C(sp²)? C(sp³) bonds.     

Synthesis of polycyclic molecules by double C(sp2)-H/C(sp3)-H arylations with a single palladium catalyst

Polycyclic molecules were obtained in good yields by double C(sp(2))-H/C(sp(3))-H arylations mediated by a single palladium/phosphine catalyst. Both double intermolecular/intramolecular and intramolecular/intramolecular C-C couplings were performed successfully, which indicates that this concept has a broad applicability for the rapid construction of molecular complexity.