7,7,8,8‐Tetraaryl‐o‐quinodimethane Stabilized by Dibenzo Annulation: A Helical π‐Electron System That Exhibits Electrochromic and Unique Chiroptical Properties

When two benzene rings are fused to a tetraaryl‐o‐quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermodynamic stability. Because the tetraarylbutadiene subunit contains electron‐donating alkoxy groups, 1 undergo reversible two‐electron oxidation to 2 ²⁺, which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e.g., sec‐butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2 b ²⁺ and 2 c ²⁺, which represents an efficient method for enhancing circular‐dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X‐ray analysis of dication 2 ²⁺ revealed π–π stacking interaction of the diarylmethylium moieties, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response.     

2-Chloroanthraquinone-catalyzed aerobic photo-oxidative synthesis of diacylamines from benzylamides

In this Letter, we report the aerobic photo-oxidative synthesis of diacylamines from benzylamides in the presence of molecular oxygen and catalytic amounts of 2-chloroanthraquinones under visible light irradiation from a fluorescent lamp.     

One‐Pot Synthesis of 2,5‐Dihydropyrroles from Terminal Alkynes,Azides, and Propargylic Alcohols by Relay Actions of Copper,Rhodium, and Gold

Relay actions of copper, rhodium, and gold formulate a one‐pot multistep pathway, which directly gives 2,5‐dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper‐catalyzed 1,3‐dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1‐sulfonyl‐1,2,3‐triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α‐allenyl‐α‐amino ketones. Finally, a gold catalyst prompts 5‐endo cyclization to produce 2,5‐dihydropyrroles.     

Homogeneous Oligomeric Ligands Prepared via Radical Polymerization that Recognize and Neutralize a Target Peptide

Abiotic ligands that bind to specific biomolecules have attracted attention as substitutes for biomolecular ligands, such as antibodies and aptamers. Radical polymerization enables the production of robust polymeric ligands from inexpensive functional monomers. However, little has been reported about the production of monodispersed polymeric ligands. Herein, we present homogeneous ligands prepared via radical polymerization that recognize epitope sequences on a target peptide and neutralize the toxicity of the peptide. Taking advantage of controlled radical polymerization and separation, a library of multifunctional oligomers with discrete numbers of functional groups was prepared. Affinity screening revealed that the sequence specificity of the oligomer ligands strongly depended on the number of functional groups. The process reported here will become a general step for the development of abiotic ligands that recognize specific peptide sequences.     

One‐Pot Synthetic Procedure for2,2′‐Disubstituted Biaryls via the Suzuki Coupling Reaction of Aryl Triflates in a Biphasic Solvent System

A one‐pot synthetic procedure for 2,2′‐disubstituted biaryls was developed via a Suzuki cross‐coupling reaction of aryl triflates in a biphasic solvent system. The effects of various bases and solvents were investigated. Results showed that the Na₂CO₃–toluene/H₂O combination gave the highest yields.     

Diisobutylaluminum hydride-promoted cyclization of silylated 1,3-dien-5-ynes: Application to total synthesis of a 20-norabietane derivative

The diisobutylaluminum hydride (DIBAL-H)-promoted benzocyclization, recently developed by this group, was adopted for the synthesis of a natural product containing a 9,10-dihydrophenanthrene skeleton to demonstrate its synthetic utility. One of the extracts from the roots of Salvia hydrangea DC. ex Bentham (Lamiaceae), a 20-norabietane derivative, was selected as the target molecule. The key step forming the 9,10-dihydrophenanthrene skeleton was achieved by the DIBAL-H-promoted cyclization of a silylated 1,3-dien-5-yne easily accessible from a substituted α-tetralone.     

Morphological studies of a hydrogen-bonded LC polymer obtained by photopolymerization in LC solvents

Anisotropic morphologies and the phase behaviour of a hydrogen-bonded LC polymer obtained by photopolymerization in two kinds of LC solvent are discussed. The hydrogen-bonded LC monomer, 4-(6-acryloyloxyhexyloxy) benzoic acid (A6OBA), was photopolymerized in 4-cyano-4′-hexyloxybiphenyl (6OCB) and in 4-cyano-4′-undecyloxybiphenyl (11OCB), which show a nematic phase and a smectic A phase, respectively. After photo-polymerization, the LC media were removed by extraction and the pure polymer was observed by scanning electron microscopy. SEM images showed that the polymer possessed fibrous morphology with a fibre diameter of a few micrometers, based on polymerization-induced phase separation. The overall geometries reflected typical LC characteristics such as schlieren and focal-conic fan textures. It was found that the hydrogen bond between benzoic acid groups in the monomer was rigid enough to fix the anisotropic phase-separated structure forming during the early stage of phase separation; however, it could not permanently maintain the fibre structure due to dissociation at elevated temperature. X-ray measurements revealed that a well developed layer structure of the hydrogen-bonded mesogen existed in the polymer obtained from the smectic phase of 11OCB, whereas a polymer layer structure could develop only partially from the nematic phase of 6OCB.