Synthesis of bitetrathiafulvalenes with FeCl3-mediated homo-coupling of tetrathiafulvalenylmagnesium bromide and formation of nanostructures from bitetrathiafulvalenes having long alkylthio chains

The FeCl₃-mediated homo-coupling of 4,5-bis(alkylthio)-4′-tetrathiafulvalenylmagnesium bromide 5 produced the corresponding bitetrathiafulvalene derivatives 2a-d in moderate yields (25-51%). Bitetrathiafulvalenes 2c and 2d having long alkylthio chains formed nanostructures and showed bulk electric conductivities (σ_rt = 2.6 − 8.0 × 10⁻⁵ S cm⁻¹) in the neutral state owing to the fastener effect. Interestingly, the nanofiber of tetrakis(dodecylthio)bitetrathiafulvalene 2d exhibited a p-type semiconductivity as detected by AFM.     

Use of Side‐Chain Incompatibility for Tailoring Long‐Range p/n Heterojunctions: Photoconductive Nanofibers Formed by Self‐Assembly of an Amphiphilic Donor–Acceptor Dyad Consisting of Oligothiophene and Perylenediimide

To tailor organic p/n heterojunctions with molecular‐level precision, a rational design strategy using side‐chain incompatibility of a covalently connected donor–acceptor (D–A) dyad has been successfully carried out. An oligothiophene–perylenediimide dyad, when modified with triethylene glycol side chains at one terminus and dodecyl side chains at the other ( 2 Amphi ), self‐assembles into nanofibers with a long‐range D/A heterojunction. In contrast, when the dyad is modified with dodecyl side chains at both termini ( 2 Lipo ), ill‐defined microfibers result. In steady‐state measurements using microgap electrodes, a cast film of the nanofiber of 2 Amphi displays far better photoconducting properties than that of the microfiber of 2 Lipo . Flash‐photolysis time‐resolved microwave conductivity measurements, in conjunction with transient absorption spectroscopy, clearly indicate that the nanofiber of 2 Amphi intrinsically allows for better carrier generation and transport properties than the microfibrous assembly of 2 Lipo .     

The first catalytic asymmetric total synthesis of ent-hyperforin

The first catalytic asymmetric total synthesis of ent-hyperforin was described here in detail. Keys to the success were a catalytic asymmetric Diels-Alder reaction, a stereoselective Clasien rearrangement, an intramolecular aldol cyclization, and a vinylogous Pummerer rearrangement. Along with the successful synthetic route, several attempted approaches toward the construction of bicyclo[3.3.1] core and the C2 oxidation were discussed.     

Characterization of subdifferentials of a singular convex functional in Sobolev spaces of order minus one

Subdifferentials of a singular convex functional representing the surface free energy of a crystal under the roughening temperature are characterized. The energy functional is defined on Sobolev spaces of order ?1, so the subdifferential mathematically formulates the energy?s gradient which formally involves 4th order spacial derivatives of the surface?s height. The subdifferentials are analyzed in the negative Sobolev spaces of arbitrary spacial dimension on which both a periodic boundary condition and a Dirichlet boundary condition are separately imposed. Based on the characterization theorem of subdifferentials, the smallest element contained in the subdifferential of the energy for a spherically symmetric surface is calculated under the Dirichlet boundary condition.     

Colloidal Stability of TiO2 Nanoparticles: The Roles of Phosphonate Ligand Length and Solution Temperature

Surface ligands are essential tools for the stabilization of colloidal nanoparticles (NPs) in solvents. However, knowledge regarding the effects of the ligand shell, especially the ligand length, is insufficient and controversial. Here we demonstrate solution-based experiments on n-alkylphosphonate-capped TiO₂ NPs to investigate the effects of ligand length and solution temperature on colloidal stability. A robust ligand-exchange process is achieved that draws free ligands and impurities away from the colloidal solution. In the case of 8 nm anatase NPs in toluene, the dodecylphosphonate ligand provided better colloidal stability than all the other n-alkylphosphonate ligands. In addition, relaxation studies suggested there is kinetic hysteresis in the dispersion/agglomeration transition. The proposed method is applicable to a wide range of surface ligands designed to maximize the colloidal stability of NPs.     

Design of a Photocatalytic [2+2] Cycloaddition Reaction Using Redox-Tag Strategy

The design of photocatalytic processes is important for a sustainable society. Key to these photocatalytic reactions is electron transfer. This article is focused on titanium dioxide photocatalyzed organic synthesis and the design of a new [2+2] cycloaddition reaction based on the electron transfer process. Electron transfer - not only between the substrate and the photocatalyst but also inter- and intramolecularly – is crucial for the reaction design. Radical cations were generated by the photocatalyst and trapped by alkenes. The resultant cyclobutyl radical cations were immediately reduced by the aryl rings via intramolecular electron transfer to obtain cyclobutane rings. The outcome of the reaction was controlled by substitution of the aryl ring and the linker connecting the aryl ring to the enol ether. The carefully designed substrates were highly effective for photocatalytic cycloaddition.     

Radical Cation Diels‐Alder Reactions of Non‐Conjugated Alkenes as Dienophiles by Electrocatalysis

Radical cation Diels‐Alder reactions provide a powerful method for the construction of six‐membered ring systems between both electron‐rich dienes and dienophiles. However, the most recent examples of this class have been limited to β‐methylstyrenes as dienophiles; the use of non‐conjugated alkenes remains challenging. The present study describes the serendipitous development of novel radical cation Diels‐Alder reactions by electrocatalysis that use non‐conjugated alkenes as dienophiles. The key to successful transformation involves highly substituted cyclohexenyl radical cations that are stable enough to be reduced by intermolecular single electron transfer.     

Preparation of 5,5-dicyano- and 5-cyano-5-ethoxycarbonyl-5,6-dihydro-3,7-diphenyl-4H-1,2-diazepines and their halogenations

5,5-Dicyano- and 5-cyano-5-ethoxycarbonyl-5,6-dihydro-3,7-diphenyl-4H-1,2-diazepines were prepared by the condensation of α-bromoacetophenone azine with malononitrile and ethyl cyanoacetate in the presence of sodium ethoxide, respectively. Halogenations of the dihydrodiazepines gave pyridazines, diazanorcaradienes, 4,4,6,6-tetrachlorodihydrodiazepines, and/or a 4-chloropyrazole whose relative yields strongly depended upon the nature of 5-substituents of the dihydrodiazepines as well as the reaction conditions.