Formal Aniline Synthesis from Phenols through Deoxygenative N‐Centered Radical Substitution

Refreshing the Legacy of Rudolf Nietzki: Benzene-1,2,4,5-tetramine and Related Compounds

Like hydroquinones and quinones, aromatic compounds with multiple NH2 groups and the corresponding quinonediimines have the potential to serve as components of useful redox-active organic materials. Benzene-1,2,4,5-tetramine (BTA) and its oxidized form BTA-H2 offer a promising redox pair of this type, and the compounds have proven to be useful in many areas of chemistry. However, key aspects of their behavior have remained poorly studied, such as the nature of their protonated forms, their preferred molecular structures, their reactivity, and their organization in condensed phases. In the present work, we have used a combination of improved methods of synthesis, computation, spectroscopic studies, and structural analyses to develop a deeper understanding of BTA, BTA-H2, their salts, and related compounds. The new knowledge is expected to accelerate exploitation of the compounds in areas of materials science where desirable properties can only be attained by properly controlling the organization of molecular components.

Synthesis of 1,2,4,5-oxadiazaboroles by three-component condensations of hydroxylamines, nitriles, and diarylborinic acids

A method for the synthesis of substituted 1,2,4,5-oxadiazaboroles is described, in which hydroxylamines, nitriles, and diarylborinic acids engage in a three-component condensation reaction. The protocol provides access to a substitution pattern that is not readily available through other methods—namely, 2,3-disubstitution, with a tetracoordinate boron center. Structures of representative members of this class of heterocycles were determined by single crystal X-ray diffraction analysis.

N-2-(Phenylamino) Benzamide Derivatives as Dual Inhibitors of COX-2 and Topo I Deter Gastrointestinal Cancers via Targeting Inflammation and Tumor Progression

Given the close association between inflammation and cancer, combining anti-inflammation therapy is prominent to improve the anticancer effect. Based on I-1, a series of agents targeting COX-2 and Topo I were designed by combining fenamates and phenols. The optimal compound 1H-30 displayed an enhanced inhibitory effect on COX-2 compared to tolfenamic acid and I-1 and showed better inhibition of Topo I than I-1. Importantly, 1H-30 showed potential anticancer effects and suppressed the activation of the NF-κB pathway in cancer cells. 1H-30 inhibited the nuclear translocation of NF-κB and suppressed the production of NO, COX-2, and IL-1β in RAW264.7. In vivo, 1H-30 showed acceptable pharmacokinetic parameters, decreased the tumor growth without affecting the body weight, down-regulated COX-2 and MMP-9, and induced apoptosis in the CT26.WT tumor-bearing mice. Accordingly, 1H-30 as a potential Topo I/COX-2 inhibitor which possessed anti-inflammatory and anticancer effects, with inhibition of the NF-κB pathway, is promising for gastrointestinal cancer therapy.

Deoxygenative gem-difluorovinylation of aliphatic alcohols

An unprecedented deoxygenative gem-difluorovinylation of aliphatic alcohols using α-trifluoromethyl alkenes is achieved under photocatalytic conditions. Inexpensive Ph₃P acts as an efficient O-atom transfer reagent to facilitate the deoxygenation of alcohols for the generation of reactive alkyl radical species. Remarkable features of this reaction include mild conditions, simple operation and broad scope. The synthetic utility of this reaction was validated by the success of two-step one-pot reactions, scale-up synthesis and chemoselective monodeoxygenation of diols.

Recent Advances in the Smiles Rearrangement: New Opportunities for Arylation

The Smiles rearrangement has undergone a renaissance in recent years providing new avenues for non-canonical arylation techniques in both the radical and polar regimes. This short review will discuss recent applications of the reaction (from 2017 to late 2021), including its relevance to areas such as heterocycle synthesis and the functionalization of alkenes and alkynes as well as glimpses at new directions for the field.

1 Introduction

2 Polar Smiles Rearrangements

3 Radical Smiles: Alkene and Alkyne Functionalization

4 Radical Smiles: Rearrangements via C–X Bond Cleavage

5 Radical Smiles: Miscellaneous Rearrangements

6 Conclusions

Aryl Transfer Strategies Mediated by Photoinduced Electron Transfer

Radical aryl migrations are powerful techniques to forge new bonds in aromatic compounds. The growing popularity of photoredox catalysis has led to an influx of novel strategies to initiate and control aryl migration starting from widely available radical precursors. This review encapsulates progress in radical aryl migration enabled by photochemical methods─particularly photoredox catalysis─since 2015. Special attention is paid to descriptions of scope, mechanism, and synthetic applications of each method.

Phosphoranyl Radical Fragmentation Reactions Driven by Photoredox Catalysis

Photocatalytic generation of phosphoranyl radicals is fast emerging as an essential method for the generation of diverse and valuable radicals, typically via deoxygenation or desulfurization processes. This Perspective is a comprehensive evaluation of all studies using phosphoranyl radicals as tunable mediators in photoredox catalysis, highlighting how two distinct methods for phosphoranyl radical formation (radical addition and nucleophilic addition) can be used to generate versatile radical intermediates with diverse reactivity profiles.

Visible light-mediated Smiles rearrangements and annulations of non-activated aromatics

Novel and efficient visible light-mediated Smiles rearrangements and annulations progressing via a radical-cation intermediate catalytically generated with an acridinium salt.