Metal-Free Mediated Meerwein-Type Reaction: A Radical Cascade Arylation/Aryl Migration/Desulfonylation of Conjugated Alkenes

A metal-free cascade arylation/aryl migration/desulfonylation of <i>N</i>-phenyl-<i>N</i>-(phenylsulfonyl)­meth­acryl­amide is described. The in situ generated diazonium salts from anilines and <i>t</i>-BuONO are used as aryl precursors. This process provides an efficient strategy for the synthesis of α-all-carbon quaternary stereocenters amides. A radical mechanism was proposed for this transformation

Dissociative Benzyl Cation Transfer versus Proton Transfer: Loss of Benzene from Protonated <i>N</i>‑Benzylaniline

In collisional activation of protonated <i>N</i>-benzylaniline, the benzene loss from the benzyl moiety is actually not the result of dissociative proton transfer (PT). In fact, benzyl cation transfer (BCT) from the nitrogen to the anilinic ring (<i>ortho</i> or <i>para</i> position) is the key step for benzene loss. Such dissociation occurs only after the benzyl group migrating from the site with the highest benzylation nucleophilicity (nitrogen) to a different one (aromatic ring carbon), which is described as dissociative benzyl cation transfer

Imine Resveratrol Analogues: Molecular Design, Nrf2 Activation and SAR Analysis

<div><p>Resveratrol is a natural phenol with protective effects against cancer and inflammation-related diseases. Its mechanism of action involves the activation of nuclear factor E2 p45-related factor 2 (Nrf2), which plays a key role in regulation of genes driven by antioxidant response element (ARE). Inspired by the effect of resveratrol, here we synthesized a series of imine resveratrol analogs (IRAs), evaluated their abilities to activate Nrf2 by using cell based ARE-reporter assay. After the first-round screening, preliminary and quantitative structure-activity relationship (SAR) was analyzed, and the structural features determining Nrf2 activation ability were proposed. Two novel IRAs were designed and subsequently synthesized, namely 2-methoxyl-3,6-dihydroxyl-IRA and 2,3,6-trihydroxyl-IRA. They were proved to be the most potent Nrf2 activators among the IRAs.</p></div

Synthesized IRAs and their effects on ARE-luciferase activity.

<p>ARE reporter cells were exposed to 7.5 µM, 15 µM or 30 µM IRA for 24 h. The value for cells treated with vehicle DMSO (0.1% v/v) was set at 1. Results are from three separate experiments.</p>a<p>Due to cytotoxicity of <b>9</b>.</p

Structures (A) and ARE-luciferase activities (B) of 33, 34 and resveratrol.

<p>ARE reporter cells were exposed to <b>33</b>, <b>34</b> and resveratrol (7.5 µM, 15 µM and 30 µM) for 24 h. The value for cells treated with vehicle DMSO (0.1% v/v) was set at 1. Results are from three separate experiments. Values shown are mean ± SD.</p

SAR results from initial screening of IRAs.

<p>SAR results from initial screening of IRAs.</p

ARE-luciferase activities in response to 6-OH IRAs.

<p>ARE reporter cells were exposed to (15 µM) for 24 h. The value for cells treated with vehicle DMSO (0.1% v/v) was set at 1. Results are from three separate experiments.</p

Proposed model for the adduct formation, fixation of IRA, and its reaction with Keap1.

<p>Proposed model for the adduct formation, fixation of IRA, and its reaction with Keap1.</p

The fragmentation mechanisms of non-covalent complex.

<p>The fragmentation mechanisms of non-covalent complex.</p

Carbon Dioxide Microbubble Bursting Ionization Mass Spectrometry

Aerosols generated by bubble bursting have been proved to promote the extraction of analytes and have ultrahigh electric fields at their water–air interfaces. This study presented a simple and efficient ionization method, carbon dioxide microbubble bursting ionization (CDMBI), without the presence of an exogenous electric field (namely, zero voltage), by simulating the interfacial chemistries of sea spray aerosols. In CDMBI, microbubbles are generated in situ by continuous input of carbon dioxide into an aqueous solution containing low-concentration analytes. The microbubbles extract low- and high-polarity analytes as they pass through the aqueous solution. Upon reaching the water–air interface, these microbubbles burst to produce charged aerosol microdroplets with an average diameter of 260 μm (8.1–10.4 nL in volume), which are immediately transferred to a mass spectrometer for the detection and identification of extracted analytes. The above analytical process occurs every 4.2 s with a stable total ion chromatogram (relative standard deviation: 9.4%) recorded. CDMBI mass spectrometry (CDMBI-MS) can detect surface-active organic compounds in aerosol microdroplets, such as perfluorooctanoic acid, free fatty acids epoxidized by bubble bursting, sterols, and lecithins in soybean and egg, with the limit of detection reaching the level of fg/mL. In addition, coupling CDMBI-MS with an exogenous voltage yields relatively weak gains in ionization efficiency and sensitivity of analysis. The results suggested that CDMBI can simultaneously accomplish both bubbling extraction and microbubble bursting ionization. The mechanism of CDMBI involves bubbling extraction, proton transfer, inlet ionization, and electrospray-like ionization. Overall, CDMBI-MS can work in both positive and negative ion modes without necessarily needing an exogenous high electric field for ionization and quickly detect trace surface-active analytes in aqueous solutions