An efficient and direct route to the synthesis of diaryl sulfoxides catalyzed by heteropoly acid

Heteropoly acid tungstophosphoric acid (H₃PW₁₂O₄₀) was found to be an excellent catalyst for the synthesis of symmetrical diaryl sulfoxides. The reaction was carried out in various organic solvents or ionic liquids and under solventfree condition. The reaction exhibited better results in terms of the yield and rate under solventfree condition. The catalyst was efficiently recovered from the reaction mixture and reused. The highlighting features of the present protocol are short reaction times, high yields of the products, ambient conditions, and simple workup.     

Acid‐Catalysed Selective Monoiodination of Electron‐Rich Arenes by Alkali Metal Iodides

Abstract

The reaction of electron‐rich arenes with alkali metal iodides such as sodium and potassium iodides in the presence of conc. H₂SO₄ gives p‐iodoarenes in high yields.     

Synthesis of functionalized diaryl sulfides based on regioselective one-pot cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes

Functionalized diaryl sulfides were prepared based on one-pot cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes.     

“First Come,First Served” and Threshold Effects in a Central-to-Planar-to-Helical Hierarchical Chiral Induction

Perylene diimide tethered pillar[5]arene derivatives form aggregates in non-polar organic solvents, and the complexation of cationic amino acid ethyl ester (cAA-OEt) with the aggregates induce a central-to-planar-to-helical chirality transfer, leading to intensive circular dichroism (CD) signals having dissymmetric factors (g_abs) of up to 3.67×10⁻². The hierarchical chiral induction exhibited an intriguing threshold dose effect, namely, the chiral induction does not occur in the low concentration range of cAA-OEt but is triggered when cAA-OEt exceeds a threshold concentration. The inhibited interconversion between the Rp and Sp conformers of pillar[5]arene, which is further restricted in the aggregation, plays a crucial role in the threshold effect. When adding enantiopure cAA-OEt first to the threshold concentration and then adding an equal amount of the antipodal cAA-OEt to give cAA-OEt in racemic form, CD spectra having the same sign as the CD induced by first adding pure cAA-OEt were induced, thus showing an unprecedented “first come, first served” effect.     

Dynamic-to-Static Planar Chirality Conversion in Pillar[5]arenes Regulated by Guest Solvents or Amplified by Crystallization

Controlling dynamic chirality and memorizing the controlled chirality are important. Chirality memory has mainly been achieved using noncovalent interactions. However, in many cases, the memorized chirality arising from noncovalent interactions is erased by changing the conditions such as the solvent and temperature. In this study, the dynamic planar chirality of pillar[5]arenes was successfully converted into static planar chirality by introducing bulky groups through covalent bonds. Before introducing the bulky groups, pillar[5]arene with stereogenic carbon atoms at both rims existed as a pair of diastereomers, and thus showed planar chiral inversion that was dependent on the chain length of the guest solvent. The pS and pR forms, regulated by guest solvents, were both diastereomerically memorized by introducing bulky groups. Furthermore, the diastereomeric excess was amplified by crystallization of the pillar[5]arene. The subsequent introduction of bulky groups yielded pillar[5]arene with an excellent diastereomeric excess (95 % de).     

A Route to Stabilize Uranium(II) and Uranium(I) Synthons in Multimetallic Complexes

Herein, we report the redox reactivity of a multimetallic uranium complex supported by triphenylsiloxide (−OSiPh₃) ligands, where we show that low valent synthons can be stabilized via an unprecedented mechanism involving intramolecular ligand migration. The two- and three-electron reduction of the oxo-bridged diuranium(IV) complex [{(Ph₃SiO)₃(DME)U}₂(μ-O)], 4 , yields the formal “U^II/U^IV”, 5 , and “U^I/U^IV”, 6 , complexes via ligand migration and formation of uranium-arene δ-bond interactions. Remarkably, complex 5 effects the two-electron reductive coupling of pyridine affording complex 7 , which demonstrates that the electron-transfer is accompanied by ligand migration, restoring the original ligand arrangement found in 4 . This work provides a new method for controlling the redox reactivity in molecular complexes of unstable, low-valent metal centers, and can lead to the further development of f-elements redox reactivity.     

Unravelling the Superiority of Nonbenzenoid Acepleiadylene as a Building Block for Organic Semiconducting Materials**

Acepleiadylene (APD), a nonbenzenoid isomer of pyrene, exhibits a unique charge-separated character with a large molecular dipole and a small optical gap. However, APD has never been explored in optoelectronic materials to take advantage of these appealing properties. Here, we employ APD as a building block in organic semiconducting materials for the first time, and unravel the superiority of nonbenzenoid APD in electronic applications. We have synthesized an APD derivative (APD-IID) with APD as the terminal donor moieties and isoindigo (IID) as the acceptor core. Theoretical and experimental investigations reveal that APD-IID has an obvious charge-separated structure and enhanced intermolecular interactions as compared with its pyrene-based isomers. As a result, APD-IID displays significantly higher hole mobilities than those of the pyrene-based counterparts. These results imply the advantages of employing APD in semiconducting materials and great potential of nonbenzenoid polycyclic arenes for optoelectronic applications.     

Photothermal Conversion by Carbon Black Facilitates Aryl Migration by Photon-Promoted Temperature Gradients

The Newman Kwart Rearrangement (NKR) offers an efficient and high-yielding method for producing substituted thiophenols from phenols. While an industrially important protocol, it suffers from high activation energy barriers (35–43 kcal/mol), requiring the use of extreme temperatures (>200 °C) and specialty equipment. This report details a highly efficient and straightforward method for facilitating the NKR using photothermal conversion. This underused, unique reactivity pathway arises from the irradiation of nanomaterials that relax via a non-radiative decay pathway to generate intense thermal gradients. We show carbon black (CB) can be an inexpensive and abundant photothermal agent under visible light irradiation to achieve a facile NKR under mild conditions. The scope includes a wide array of stereo- and electronically diverse substrates with increasing difficulty of rearrangement, including BHT and BINOL as effective substrates. Furthermore, we demonstrate the unique application for temporal control in a thermal reaction and tunability of thermal gradients by modulating light intensity. Ultimately, photothermal conversion enables high-temperature reactions with simple, visible light irradiation.     

Regioselective synthesis of amino- and nitroarenes based on [3+3] cyclocondensations of 1,3-bis(silyloxy)-1,3-butadienes

Functionalized amino- and nitro-substituted biaryls and dibenzo[b,d]pyrid-6-ones (6(5H)-phenanthridinones) were prepared by [3+3]cyclocondensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with nitro-substituted 1-aryl-1-silyloxy-1-en-3-ones and subsequent hydrogenation. 4-Nitro- and 4-aminophenols were prepared based on formal [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-ethoxy-2-nitro-2-en-1-ones.     

The Directed Synthesis of Biaryl Compounds: Modern Concepts and Strategies

The preparation and utilization of specific biaryl systems, particularly those which suffer hindered rotation, is a demanding goal not only in the synthesis of natural products and Pharmaceuticals, but also for example in the discovery of new reagents for asymmetric synthesis. This article will attempt to provide a topical review of modern, efficient processes for the specific preparation of biaryls. This appears to be of particular urgency, since, under the pressure of continually increasing demand, a wealth of new or modified synthetic approaches to the ever more important biaryl systems has been realized in recent years. The high standard which has been reached in this field is impressively demonstrated by regio- and stereoselective syntheses of important biaryl natural products such as steganone, ancistrocladine, ancistrocladisine, and dioncophylline A. Besides the utilization of asymmetric induction in the actual coupling step, the thermodynamically or kinetically controlled torsion of biaryl axes belongs to the most important concepts discussed.