Poly[(μ‐pentafluorobenzoato‐κ2O:O′)(pentafluorobenzoato‐κO)(μ‐pyrazine‐κ2N:N′)copper(II)]: a coordination polymer linked into a three‐dimensional network by intermolecular C—H...F—C interactions

In the title compound, [Cu(C₆F₅COO)₂(C₄H₄N₂)]_n, (I), the asymmetric unit contains one Cu^II cation, two anionic pentafluorobenzoate ligands and one pyrazine ligand. Each Cu^II centre is five‐coordinated by three O atoms from three independent pentafluorobenzoate anions, as well as by two N atoms from two pyrazine ligands, giving rise to an approximately square‐pyramidal coordination geometry. Adjacent Cu^II cations are bridged by a pyrazine ligand and two pentafluorobenzoate anions to give a two‐dimensional layer. The layers are stacked to generate a three‐dimensional supramolecular architecture via strong intermolecular C—H...F—C interactions, as indicated by the F...H distance of 2.38 Å.     

O‐Alkyl S‐3,3‐Dimethyl‐2‐oxobutyl Dithiocarbonates as Versatile Sulfur‐Transfer Agents in Radical C(sp3)?H Functionalization

Boiling of the title compounds in ethereal solvents or cycloalkanes in the presence of a radical initiator leads to radical C(sp³)? H functionalization, by which a sulfur atom is introduced into the ethereal solvents at the oxygenated carbon atom or into the cycloalkanes. Both acyclic and cyclic ethers, such as [18]crown‐6 and [D₈]THF, undergo the sulfur transfer. The reaction is useful for the synthesis of monothioacetals, thiols, and sulfides from simple starting materials.     

Cu(OAc)2‐catalyzed partial oxidation of methane to methyl trifluoroacetate in the liquid phase

Simple transition‐metal salts were investigated as the catalysts for the partial oxidation of methane. In trifluoroacetic acid (TFA), methane could be efficiently converted to methyl trifluoroacetate by the Cu(OAc)₂/K₂S₂O₈ catalyst system. A quantitative yield (96.3%) based on methane has been obtained under the optimized conditions. A possible mechanism involving radical intermediates has been suggested for this reaction. Copyright © 2000 John Wiley & Sons, Ltd.     

Rhodium(III)/Copper(II)‐Promoted trans‐Selective Heteroaryl Acyloxylation of Alkynes: Stereodefined Access to trans‐Enol Esters

Enol esters are versatile synthetic building blocks which can be elaborated by a wide variety of transformations. The classical synthesis by O‐selective enolate acylation often hampers control of the E/Z selectivity with highly substituted substrates. A rhodium(III)/copper(II)‐mediated process is reported to provide tetrasubstituted enol esters in a trans‐selective fashion. Overall, the reaction consists of a heteroaryl acyloxylation of alkynes. The process is initiated by a rhodium(III)‐catalyzed C2‐selective activation of electron‐rich heteroarenes, such as benzofuran, furan, and thiophene. Upon addition across an alkyne, a transmetalation to copper(II) enables reductive C? O bond formation. The transformation allows the three‐component couplings of heteroarenes, alkynes, and carboxylic acids. Application of the method in the functionalization of bioactive furocoumarin natural products is also described.     

Stereoretentive Copper‐Catalyzed Directed Thioglycosylation of C(sp2)−H Bonds of Benzamides

An efficient thioglycosylation of C(sp²)?H bonds with thiosugars has been established for the first time. Using only Cu(OAc)₂?H₂O as a catalyst and Ag₂CO₃ as an additive in DMSO, the protocol proved to have broad scope, and a variety of complex thioglycosides have been prepared in good yields with exclusive β‐selectivity.     

Synthesis,crystal structure and docking studies of tetracyclic 10‐iodo‐1,2‐dihydroisoquinolino[2,1‐b][1,2,4]benzothiadiazine 12,12‐dioxide and its precursors

The title compound, 10‐iodo‐1,2‐dihydroisoquinolino[2,1‐b][1,2,4]benzothiadiazine 12,12‐dioxide, C₁₅H₁₁IN₂O₂S ( 8 ), was synthesized via the metal‐free intramolecular N‐iodosuccinimide (NIS)‐mediated radical oxidative sp³‐C—H aminative cyclization of 2‐(2′‐aminobenzenesulfonyl)‐1,3,4‐trihydroisoquinoline, C₁₅H₁₆N₂O₂S ( 7 ). The amino adduct 7 was prepared via a two‐step reaction, starting from the condensation of 2‐nitrobenzenesulfonyl chloride ( 4 ) with 1,2,3,4‐tetrahydroisoquinoline ( 5 ), to afford 2‐(2′‐nitrobenzenesulfonyl)‐1,3,4‐trihydroisoquinoline, C₁₅H₁₄N₂O₄S ( 6 ), in 82% yield. The catalytic hydrogenation of 6 with hydrogen gas, in the presence of 10% palladium‐on‐charcoal catalyst, furnished 7 . Products 6 – 8 were characterized by their melting points, IR and NMR (¹H and ¹³C) spectroscopy, and single‐crystal X‐ray diffraction. The three compounds crystallized in the monoclinic space group, with 7 exhibiting classical intramolecular hydrogen bonds of 2.16 and 2.26 Å. All three crystal structures exhibit centrosymmetric pairs of intermolecular C—H…π(ring) and/or π–π stacking interactions. The docking studies of molecules 6 , 7 and 8 with deoxyribonucleic acid (PDB id: 1ZEW ) revealed minor‐groove binding behaviours without intercalation, with 7 presenting the most favourable global energy of the three molecules. Nonetheless, molecule 8 interacted strongly with the DNA macromolecule, with an attractive van der Waals energy of ?15.53 kcal mol^?1.     

Two new isatin derivatives: 1‐benzyl‐4,5,6‐trimethoxyindoline‐2,3‐dione and 1‐benzyl‐5‐fluoroindoline‐2,3‐dione

Isatin (1H‐indole‐2,3‐dione) derivatives represent synthetically useful substrates which can be used to prepare a broad range of heterocyclic compounds. In the title compounds, C₁₈H₁₇NO₅, (I), and C₁₅H₁₀FNO₂, (II), the isatin ring systems are planar and form a dihedral angle of 73.04 (7)° in (I) and 76.82 (11)° in (II) with the benzyl groups. The bicyclic scaffolds in both compounds are almost superimposable, with an r.m.s. deviation of 0.061 Å. The crystal structures of both derivatives are stabilized by C—H...O interactions. These contacts generate an R¹₂(7) ring motif in (I) and a C(7) chain motif in (II).     

Hydrogen bonding between aromatic H and F groups leading to a stripe structure with R‐ and S‐columns: the crystal structure of (2,7‐dimethoxynaphthalen‐1‐yl)(3‐fluorophenyl)methanone and comparison with its 1‐aroylnaphthalene analogues

In the molecule of (2,7‐dimethoxynaphthalen‐1‐yl)(3‐fluorophenyl)methanone, C₁₉H₁₅FO₃, (I), the dihedral angle between the plane of the naphthalene ring system and that of the benzene ring is 85.90 (5)°. The molecules exhibit axial chirality, with either an R‐ or an S‐stereogenic axis. In the crystal structure, each enantiomer is stacked into a columnar structure and the columns are arranged alternately to form a stripe structure. A pair of (methoxy)C—H...F hydrogen bonds and π–π interactions between the benzene rings of the aroyl groups link an R‐ and an S‐isomer to form a dimeric pair. These dimeric pairs are piled up in a columnar fashion through (benzene)C—H...O=C and (benzene)C—H...OCH₃ hydrogen bonds. The analogous 1‐benzoylated compound, namely (2,7‐dimethoxynaphthalen‐1‐yl)(phenyl)methanone [Kato et al. (2010). Acta Cryst. E 66 , o2659], (II), affords three independent molecules having slightly different dihedral angles between the benzene and naphthalene rings. The three independent molecules form separate columns and the three types of column are connected to each other via two C—H...OCH₃ hydrogen bonds and one C—H...O=C hydrogen bond. Two of the three columns are formed by the same enantiomeric isomer, whereas the remaining column consists of the counterpart isomer. In the case of the fluorinated 1‐benzoylated naphthalene analogue, namely (2,7‐dimethoxynaphthalen‐1‐yl)(4‐fluorophenyl)methanone [Watanabe et al. (2011). Acta Cryst. E 67 , o1466], (III), the molecular packing is similar to that of (I), i.e. it consists of stripes of R‐ and S‐enantiomeric columns. A pair of C—H...F hydrogen bonds between R‐ and S‐isomers, and C—H...O=C hydrogen bonds between R(or S)‐isomers, are also observed. Consequently, the stripe structure is apparently induced by the formation of R...S dimeric pairs stacked in a columnar fashion. The pair of C—H...F hydrogen bonds effectively stabilizes the dimeric pair of R‐ and S‐enantiomers. In addition, the co‐existence of C—H...F and C—H...O=C hydrogen bonds makes possible the formation of a structure with just one independent molecule.     

Ir(III)‐Catalyzed C7‐Position‐Selective Oxidative CH Alkenylation of Indolines with Alkenes in Air

An efficient method for C7‐position‐selective alkenylation of N‐substituted indolines with alkenes is reported. Various 7‐alkenylindolines were obtained in moderate to excellent yields in air in the presence of catalytic amounts of [Cp*IrCl₂]₂, AgOTf, and Cu(OAc)₂. The protocol relies on the use of a carbonyl or carbamoyl group on the nitrogen atom of indoline as a directing group and is potentially applicable to the synthesis of 7‐alkenylindoles and 7‐alkylindoles.     

Aryl(triethyl)silanes for Biaryl and Teraryl Synthesis by Copper(II)‐Catalyzed Cross‐Coupling Reaction

Aryl(triethyl)silanes are found to undergo cross‐coupling with iodoarenes in the presence of catalytic amounts of CuBr₂ and Ph‐Davephos, as well as cesium fluoride as a stoichiometric base. Because the silicon reagents are readily accessible through catalytic C?H silylation of aromatic substrates, the net transformation allows coupling of aromatic hydrocarbons with iodoarenes via triethylsilylation.     

Synthesis of Functionalized (η5‐Indenyl)rhodium(III) Complexes and Their Application to C−H Bond Functionalization

It has been established that reductive complexation of functionalized benzofulvenes, which are readily prepared from commercially available indene and 2‐methylindene, with RhCl₃ in ethanol affords the corresponding indenyl–rhodium(III) dichlorides bearing substituents at the 1‐ (H or CO₂Et), 2‐ (H or Me), and 3‐ [CH₂Ph or CH₂(2‐MeOC₆H₄)] positions. The indenyl–rhodium(III) complexes bearing one ethoxycarbonyl group showed higher thermal stability and regioselectivity than our previously reported Cp^ERh^III complex toward the oxidative [3+2] annulation of acetanilides with internal alkynes.     

Enantioselective Synthesis of Spiroindenes by Enol‐Directed Rhodium(III)‐Catalyzed CH Functionalization and Spiroannulation

Chiral cyclopentadienyl rhodium complexes promote highly enantioselective enol‐directed C(sp²)‐H functionalization and oxidative annulation with alkynes to give spiroindenes containing all‐carbon quaternary stereocenters. High selectivity between two possible directing groups, as well as control of the direction of rotation in the isomerization of an O‐bound rhodium enolate into the C‐bound isomer, appear to be critical for high enantiomeric excesses.     

Dimers linked by type‐I C—F...F—C contacts in (Z)‐3‐methyl‐4‐[2‐(4‐methylphenyl)hydrazinylidene]‐1‐(pentafluorophenyl)‐1H‐pyrazol‐5(4H)‐one

The title compound, C₁₇H₁₁F₅N₄O, is described and compared with two closely related analogues in the literature. There are two independent molecules in the asymmetric unit, linked by N—H...O hydrogen bonds and π–π interactions into dimeric entities, presenting a noticeable noncrystallographic C₂ symmetry. These dimers are in turn linked by a medium‐strength type‐I C—F...F—C interaction into elongated tetramers. Much weaker C—H...F contacts link the tetramers into broad two‐dimensional substructures parallel to (101).     

Palladium‐Catalyzed Formal [4+2] Cycloaddition of Benzoic and Acrylic Acids with 1,3‐Dienes via C—H Bond Activation: Efficient Access to 3,4‐Dihydroisocoumarin and 5,6‐Dihydrocoumalins

We report a palladium‐catalyzed formal intermolecular [4+2] cycloaddition of benzoic and acrylic acids with 1,3‐dienes including the stock chemicals 1,3‐butadiene and isoprene leading to synthetically useful 3,4‐dihydroisocoumarins and 5,6‐dihydrocoumalins. Stepwise C—H bond cleavage and annulation are likely involved in the reaction pathway. The synthetic potential of the methodology was demonstrated by two short derivatizations and total synthesis of natural product Clausamine B.     

Azaruthena(II)‐bicyclo[3.2.0]heptadiene: Key Intermediate for Ruthenaelectro(II/III/I)‐catalyzed Alkyne Annulations

A ruthenium‐catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes has been established, enabling the preparation of various bridgehead N‐fused [5,6]‐bicyclic heteroarenes through regioselective electrochemical C?H/N?H annulation without chemical metal oxidants. Novel azaruthenabicyclo[3.2.0]heptadienes were fully characterized and identified as key intermediates. Mechanistic studies are suggestive of an oxidatively induced reductive elimination pathway within a ruthenium(II/III) regime.     

Rhodium(III)‐Catalyzed Annulation of 2‐Alkenyl Anilides with Alkynes through C−H Activation: Direct Access to 2‐Substituted Indolines

A Rh^III complex featuring an electron‐deficient η⁵‐cyclopentadienyl ligand catalyzed an unusual annulation between alkynes and 2‐alkenyl anilides to form synthetically appealing 2‐substituted indolines. Formally, the process can be viewed as an allylic amination with concomitant hydrocarbonation of the alkyne. Mechanistic experiments indicate that this transformation involves an unusual rhodium migration with a concomitant 1,5‐H shift.     

Intermolecular Amination of Unactivated C(sp3)−H Bonds with Cyclic Alkylamines: Formation of C(sp3)−N Bonds through Copper/Oxygen‐Mediated C(sp3)−H/N−H Activation

The first example of intermolecular amination of unactivated C(sp³)?H bonds by cyclic alkylamines mediated by Cu(OAc)₂/O₂ is reported. This method avoids the use of benzoyloxyamines as the aminating reagent, which are normally prepared from alkylamines in extra steps. A variety of unnatural β^{2, 2}‐amino acid analogues are synthesized by this simple and efficient procedure. This approach offers a solution to the previous unmet challenge of C(sp³)?H/N?H activation for the formation of C(sp³)?N bonds.     

Palladium‐mediated Cleavage of S–C Bonds: Preparation and Characterization of Palladium(II) Complexes of 2, 6‐Diformyl‐4‐tert‐butylthiophenol Dioxime

The synthesis of air‐sensitive 2, 6‐diformyl‐4‐tert‐butylthiophenol dioxime H₃L3 was achieved by a Pd‐mediated S–C cleavage of the corresponding S‐tert‐butyl protected thioether. The novel ligand forms a dinuclear, neutral Pd^II₂ complex, which is stabilized by two N ··· HO hydrogen bonds to give a pseudo‐macrocyclic structure. The crystal structure of a Pd^II complex of an oxidized isothiazole derivative of H₃L3 is also reported.     

Direct C—H Bond Activation of Benzoxazole and Benzothiazole with Aryl Bromides Catalyzed by Palladium(II)‐N‐heterocyclic Carbene Complexes

Herein, we report that a series of novel palladium(II)‐NHC complexes (NHC=N‐heterocyclic carbene) were synthesized. The structures of all novel complexes were characterized by ¹H NMR, ¹³C NMR, FT‐IR spectroscopy and elemental analysis techniques. These palladium(II)‐NHC complexes were tested as efficient catalysts in the direct C—H bond activation of benzoxazole and benzothiazole with aryl bromides in the presence of 1 mol% catalyst loading at 150 °C for 4 h. Under the given conditions, various aryl bromides were successfully applied as the arylating reagents to achieve the 2‐arylbenzoxazoles and 2‐arylbenzothiazoles in acceptable to high yields.     

Synthesis of Chiral β‐Lactams by Pd‐Catalyzed Enantioselective Amidation of Methylene C(sp3)–H Bonds Enabled by a 2‐Pyridylisopropyl Auxiliary†

Qiang Yue, Xu Yang, Meng‐Xue Jiang, Bing‐Feng Shi, Tao Zhou, Yi Ding and Ye‐Qiang Han (from left to right). Mr. Tao Zhou is currently a postdoctoral fellow in the group of Prof. Bing‐Feng Shi in Zhejiang University. Mr. Ye‐Qiang Han is currently a fourth‐year PhD student in the group of Prof. Bing‐Feng Shi in Zhejiang University.