Iron‐Catalyzed Aminative Cyclization/Intermolecular Homolytic Aromatic Substitution Using Oxime Esters and Simple Arenes

Intermolecular C?H alkylation of simple arenes in the presence of an iron catalyst has been achieved in a cascade manner with an aminative cyclization triggered by N?O bond cleavage of an alkene‐tethered oxime ester. Various arenes, including electron‐rich and electron‐poor arenes, and heteroarenes can be employed in the reaction system. Regioselectivity and radical trapping experiments support the involvement of alkyl radical species, which undergo a homolytic aromatic substitution (HAS) to afford the arylation products.     

Metal-free synthesis of azacalix[4]arenes

The facile preparation of N(H)-bridged azacalix[4]arenes has been achieved by stepwise nucleophilic aromatic substitutions assisted by hydrogen bonding interactions. The synthesis is uncatalyzed and affords previously unknown tetranitroazacalix[4]arenes.     

Palladium-catalyzed direct coupling reaction of propargylic alcohols with arylboronic acids

The direct coupling of propargylic alcohols with arylboronic acids has been achieved using palladium catalyst. Various propargylic alcohols and arylboronic acids can be coupled to afford the corresponding allenic and propargylic arenes, which are selectively produced depending on the substituent on the propargylic alcohol, respectively.     

Silver‐Promoted Oxidative Benzylic C−H Trifluoromethoxylation

A silver‐promoted oxidative benzylic C?H trifluoromethoxylation has been reported for the first time. With trifluoromethyl arylsulfonate as the trifluoromethoxylation reagent, various arenes, having diverse functional groups, undergo trifluoromethoxylation of their benzylic C?H bonds to form trifluoromethyl ethers under mild reaction conditions. In addition, the trifluoromethoxylation and the fluorination of methyl groups of electron‐rich arenes have been achieved to prepare α‐fluorobenzyl trifluoromethyl ethers in one step.     

Copper-catalyzed oxidative trifluoromethylation of terminal alkynes and aryl boronic acids using (trifluoromethyl)trimethylsilane

Trifluoromethylated acetylenes and arenes are widely applicable in the synthesis of pharmaceuticals and agrochemicals. In 2010, our group has reported the copper-mediated oxidative trifluomethylation of terminal alkynes and aryl boronic acids. This method allows a wide range of functional group tolerant trifluoromethylated acetylenes and arenes to be easily prepared. After the preliminary mechanistic studies of the oxidative trifluoromethylation of terminal alkyne, an efficient copper-catalyzed oxidative trifluoromethylation of terminal alkynes and aryl boronic acids has been developed. The catalytic protocol is successfully achieved by adding both the substrate and a portion of CF(3)TMS slowly using a syringe pump to the reaction mixture.     

Synthesis of chiral calix[4]arenes bearing tartaric ester moieties

The synthesis of chiral calix[4]arenes with tartaric acid ester moieties has been achieved by the reactions of tartaric ester chloroacetates with calix[4]arenes in moderate yields. All the chiral calix[4]arene derivatives are in a cone conformation according to the ¹H NMR doublet–doublet pattern of the protons of the methylene groups between the phenol rings. The results of NMR and specific rotations indicate that the molecules have C₂ symmetry with asymmetric features.     

Convenient Method for Dehalogenation of Aryl Halides

Reductive dehalogenation of aryl halides was achieved using hydrogen and a palladium catalyst. By using deuterium gas, the deuterated arenes were readily prepared.     

Regioselective O-substitution of p-tert-butylcalix[7]arene

[structure: see text]. The first examples of selectively functionalized calix[7]arenes have been obtained by weak-base promoted O-alkylation or O-benzoylation of p-tert-butylcalix[7]arene. Mono-, 1,3- and 1,4-disubstituted calix[7]arenes have been obtained in workable yields, while the 1,2,4,6-tetrasubstitution was achieved with surprisingly high selectivity (50-88% yield) by using K2CO3 as base. A rationale for this finding is proposed.     

Ruthenium(II)‐Catalyzed Oxidative CH Alkenylations of Sulfonic Acids,Sulfonyl Chlorides and Sulfonamides

Twofold C?H functionalization of aromatic sulfonic acids was achieved with an in situ generated ruthenium(II) catalyst. The optimized cross‐dehydrogenative alkenylation protocol proved applicable to differently substituted arenes and a variety of alkenes, including vinyl arenes, sulfones, nitriles and ketones. The robustness of the ruthenium(II) catalyst was demonstrated by the chemoselective oxidative olefination of sulfonamides as well as sulfonyl chlorides. Mechanistic studies provided support for a reversible, acetate‐assisted C?H ruthenation, along with a subsequent olefin insertion.     

Open‐tubular capillary electrochromatography using carboxylatopillar[5]arene as stationary phase

Pillar[n]arenes have achieved much interest in material chemistry and supramolecular chemistry due to unusual pillar shape structure and high selectivity toward guest. However, pillar[n]arenes have not yet been applied in capillary electrochromatography. This work at first time reports that carboxylatopillar[5]arene is used as a stationary phase in open‐tubular capillary electrochromatography. Carboxylatopillar[5]arene not only possess the advantages of pillar[n]arenes but also provide free carboxy groups for immobilizing on the inner wall of capillary column via covalent bonding. The characterization of SEM and FT‐IR indicated that carboxylatopillar[5]arene was successfully grafted on the inner wall of capillary. The baseline separation of model analytes including neutral, basic, and acidic compounds, nonsteroidal anti‐inflammatory drugs and dansyl‐amino acids have been achieved thanks to the electron‐rich cavity of carboxylatopillar[5]arene and hydrophobic interactions between the analytes and stationary phase. The intraday, interday, and column‐to‐column precisions (RSDs) of retention time and peak area for the neutral analytes were all less than 3.34 and 9.65%, respectively. This work indicates that pillar[n]arenes have great potential in capillary electrochromatography as novel stationary phase.     

First total synthesis of cassiarin A, a naturally occurring potent antiplasmodial alkaloid

The first total synthesis of cassiarin A, an antiplasmodial alkaloid isolated from Cassia siamea, was achieved via sequential alkynylation of arenes with Sonogashira coupling and 6- endo-dig-cyclization of phenolic oxygens to the resulting alkynes.     

Polymer Acceptors for High-Performance All-Polymer Solar Cells

All-polymer solar cells (all-PSCs) have attracted considerable attention owing to their pronounced advantages of excellent mechanical flexibility/stretchability and greatly enhanced device stability as compared to other types of organic solar cells (OSCs). Thanks to the extensive research efforts dedicated to the development of polymer acceptors, all-PSCs have achieved remarkable improvement of photovoltaic performance, recently. This review summarizes the recent progress of polymer acceptors based on the key electron-deficient building blocks, which include bithiophene imide (BTI) derivatives, boron-nitrogen coordination bond (B←N)-incorporated (hetero)arenes, cyano-functionalized (hetero)arenes, and fused-ring electron acceptors (FREAs). In addition, single-component-based all-PSCs are also briefly discussed. The structure-property correlations of polymer acceptors are elaborated in detail. Finally, we offer our insights into the development of new electron-deficient building blocks with further optimized properties and the polymers built from them for efficient all-PSCs.     

Rim-differentiated pillar[5]arenes

Pillar[5]arenes, designed and prepared by Ogoshi et al. in 2008 initially, refer to fifth classical macrocyclics. Among a wide range of pillar[5]arenes, rim-differentiated pillar[5]arenes containing five identical substituents on one rim and five different identical groups on the other rims are considered the most noteworthy type of pillar[5]arenes. As compared with the perfunctionalized pillar[5]arene, the self-assembly properties of rim-differentiated pillar[5]arenes have more varieties. On the other hand, in comparison with other types of pillar[5]arenes, the rim-differentiated pillar[5]arenes exhibit a more rigid symmetrical structure. In the present review, the synthetic methods, host-guest interactions, self-assembly properties and applications of rim-differentiated pillar[5]arenes are summarized. Hopefully, this review will be conducive to researchers in macrocyclic supramolecular chemistry.     

Self-recognition, structure, stability, and guest affinity of pyrogallol[4]arene and resorcin[4]arene capsules in solution

In the present study, we used diffusion NMR to probe the structures and characteristics of the products obtained from the self-assembly of resorcin[4]arenes 1a and 1b and pyrogallol[4]arenes 2a and 2b in CDCl(3) solutions. It was found that all four molecules self-assemble into hexameric capsules. The hexameric capsules of pyrogallol[4]arenes 2a and 2b were found to be more stable than the capsules of resorcin[4]arenes 1a and 1b in polar media. We also studied the role of water molecules in the self-assembly of the different capsules and found that water molecules are part of the hexameric capsules of resorcin[4]arenes 1a and 1b but not in the capsules of pyrogallol[4]arenes 2a and 2b. It was found that the self-assembly process between the resorcin[4]arenes and pyrogallol[4]arenes proceeds with self-recognition. When mixing two macrocycles of different types in a chloroform solution, no heterohexamers are formed, only the capsule constructed from the same macrocycle is detected. However, when two resorcin[4]arenes (i.e., 1a and 1b) or two pyrogallol[4]arenes (i.e., 2a and 2b) are mixed, heterohexamers are formed over time. In addition, we found that resorcin[4]arenes and pyrogallol[4]arenes differ significantly in their guest affinity. The capsules of 1a and 1b can accommodate both the tertiary alkylamines and their respective ammonium salts, while the capsules of 2a and 2b encapsulate only the neutral tertiary alkylamines.     

Metal-catalyzed reactions of diborons for synthesis of organoboron compounds

Metal-catalyzed borylation of alkenes, alkynes, arenes, and organic halides with B-B or H-B compounds has been developed for the synthesis of organoboron compounds from simple organic substrates. The platinum(0)-catalyzed addition of bis(pinacolato)diboron to alkenes and alkynes provided a method for the stereoselective synthesis of cis-bis(boryl)alkanes or cis-bis(boryl)alkenes. The addition of diboron to 1,3-dienes with platinum(0) complexes provided a new access to cis-1,4-bis(boryl)-2-butene derivatives, which are versatile reagents for diastereoselective allylboration of carbonyl compounds. The first one-step procedure for the syntheses of aryl-, vinyl-, and allylboronates was achieved via crosscoupling reactions of diborons with aryl and 1-alkenyl halides or triflates and allyl acetates. Direct C-H borylation of arenes catalyzed by a transition metal complex was studied as an economical protocol for the synthesis of a variety of arylboron derivatives. Ir-catalyzed C-H borylation of arenes, heteroarenes, and benzylic positions of alkylarenes by bis(pinacolato)diboron or pinacolborane furnished aryl-, heteroaryl-, and benzylboron compounds. This article discusses the mechanisms of these reactions and their synthetic applications.     

Cationic Pd(II)/bipyridine-catalyzed addition of arylboronic acids to arylaldehydes. One-pot synthesis of unsymmetrical triarylmethanes

Cationic Pd(II) complex-catalyzed addition of arylboronic acids to aldehydes with low catalyst loading was developed with high yields. One-pot synthesis of unsymmetrical triarylmethanes from arylboronic acids, aryl aldehydes, and electron-rich arenes was achieved in high yields.     

Synthesis and inclusion properties of pillar[n]arenes

A detailed study of the reaction conditions revealed that a quantitative cyclocondensation of 1,4-dialkoxy-2,5-bis(alkoxymethyl)-benzenes to pillar[n]arenes can be achieved by catalysis of p-toluenesulfonic acid in CH₂Cl₂. Major product of this new reaction is in each case a cyclopentamer (n = 5), but small amounts of the pillar[n]arenes with n = 6, 7 and 10 can be obtained as well. Different alkoxy groups in 1- and 4-position lead to regioisomers. All cyclooligomers exist in pillar structures as pair of enantiomers, which show a racemisation at room temperature, which is fast in terms of the NMR time scale. The racemisation process occurs by rotation of the 1,4-phenylene segments in the macrocyclic rings. Pillar[n]arenes exhibit novel host–guest behavior.     

Enantioselective friedel-crafts alkylations with benzoylhydrazones promoted by a simple strained silacycle reagent

The enantioselective Friedel-Crafts reaction of electron-rich arenes and heteroarenes with the benzoylhydrazone of isopropyl glyoxylate mediated by a simple chiral silane Lewis acid is described. The reactions are highly practical, as demonstrated by a larger scale (5 g of the hydrazone) reaction in which the recovery of the pseudoephedrine in 99% yield was achieved. A simple model is advanced to explain the observed enantioselectivity.     

A simple and highly effective method for hydrogenation of arenes by [Rh(COD)Cl]2

Hydrogenation of arenes, including chiral BINOLs and the lignin model compounds, has been achieved efficiently by using the simple complex [Rh(COD)Cl]₂ as catalyst precursor.     

Rhodium-catalyzed C-H activation and conjugate addition under mild conditions

An efficient rhodium(III)-catalyzed C-H activation and subsequent conjugate addition was achieved under mild conditions. The reaction utilized inert arenes to replace stoichiometric organometallic reagents and can tolerate various functional groups as well as air and water.