Philip Wai Hong Chan

Dichloramine-T (DCT) and dibromamine-T (DBT) are versatile N,N-dihalo-p-toluenesulfonamides that occupy a unique position at the interface of ionic, radical and nitrene transfer chemistry. Although traditionally viewed as powerful electrophilic halogenating reagents, these compounds have found use in a diverse range of reactions, enabling transformations such as the aziridination, halogenation, oxidation and vicinal halofunctionalisation of a vast range of structurally diverse molecules. Over the past several decades, advances in photochemistry, radical chemistry and transition metal catalysis have significantly expanded the utility of these reagents, transforming them from simple oxidants into powerful tools in modern organic synthesis. This review provides a comprehensive overview of the reaction chemistry of DCT and DBT, examining their often-unique reactivity and mechanistic behaviour.

An efficient site-selective protocol for the 4CzPN-catalyzed 1,2-diamination of aldehydes by amines and α -silylamines under visible light reaction conditions at room temperature is described. The generality of the sustainable modular...

Copper-catalyzed methods for the halogenation of unactivated C(sp³)–H bonds has emerged as a powerful tool in modern chemical synthesis. Their rapid and elegant development has been driven by recent advances in radical and redox chemistry. This account provides an overview of these recent efforts in copper-mediated unactivated C(sp³)–H halogenation strategies that have focused and exploited mechanistic paradigms such as inter- and intra-hydrogen-atom transfer reactions and Cu(I)/Cu(II)/Cu(III) redox cycling. Received: 02 December 2025 Accepted after revision: 19 January 2026 Article published online: 05 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

The selective incorporation of nitrogen into organic molecules remains a central challenge in modern synthetic chemistry, particularly when aiming to access complex, functionalized scaffolds under mild and sustainable conditions. In this report, we describe a photocatalytic method that employs hydroxylamine‐derived nitrene precursors and unprotected sulfinamides under mild conditions, enabling efficient nitrene transfer without the need for stoichiometric amounts of an oxidant. The resulting unprotected sulfonimidamides serve not only as target compounds but also as versatile intermediates for further nitrene‐transfer reactions, affording complex sulfur–nitrogen‐rich frameworks. Mechanistic studies support a photoinduced single‐electron transfer process involving a reactant complex between the photocatalyst and nitrene precursor. This work establishes a general and modular platform for accessing challenging architectures based on sulfonimidamides, expanding the toolkit for late‐stage functionalization and heteroatom‐rich molecule construction.

A protocol for the efficient and expeditious synthesis of the pentacyclic C2-spiropseudoindoxyl scaffold that relies on a copper(I)-catalyzed 6-endo-dig cycloaddition/internal redox (IR)/anthranil formation/oxaziridine formation/ring-opening spirocyclization/reduction cascade of 1H-indole N-tethered o-alkynylnitroarenes is described.

The rapid emergence of antimicrobial resistant Gram-negative bacteria compromises current antibiotic efficacy, including the last-resort antibiotic polymyxins, emphasizing the urgent need for novel therapeutic strategies. Nanoscale-based antimicrobials exhibit potential as an alternative treatment strategy. In this study, four furoxan-based nitric oxide (NO)-releasing nanoparticles (NPs) were prepared and their antimicrobial efficacy was tested against different Gram-negative bacteria, including: Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli via minimum inhibitory testing, where NPs exhibited selective activity against lipopolysaccharide (LPS)-deficient A. baumannii strains and LPS-truncated strains tested. Advanced microscopic techniques and mechanistic investigations using model membranes mimicking the LPS-deficient A. baumannii membrane and LPS-containing membrane, via neutron reflectometry and small-angle neutron scattering, indicated that the NPs specifically destabilize the LPS-deficient A. baumannii membrane, leading to the release of cellular content. This work provides mechanistic insight into the selective activity of the NPs against LPS-deficient A. baumannii and their lack of efficacy in strains with LPS, highlighting membrane-level determinants that may inform future antimicrobials development.

An efficient and expeditious method to assemble oxa-bridged polycycles bearing up to six contiguous stereocenters from a gold(I)-catalyzed [3 + 2] cycloaddition/unactivated C(sp³)-H bond insertion cascade of o-1,6-enynyl benzaldehydes at a low catalyst loading of 2 mol % is described.

A synthetic method that enables the site-selective fluorination at an unactivated C(sp³)-H bond located two to six C-C bond distances from the C═O group in ketones, carboxylic esters, and amides by Selectfluor [1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)] aided by a copper(I) salt is described. The site selectivity of the C(sp³)-F bond formation protocol was exemplified by the late-stage functionalization of five natural product and drug molecule derivatives.

A synthetic method to prepare δ–κ‐chloroketones, ‐esters and ‐amides that relies on the copper(I)‐mediated chlorination at the unactivated tertiary δ–κ‐C(sp³)−H bond of ketones, carboxylic esters, and amides by dichloramine‐T is presented. By exploiting the ability of the N‐chloramide to act as both the hydrogen atom transfer (HAT) and chlorination reagent, the reactions were shown to be site‐selective with halogenation only occurring at the unactivated tertiary carbon center situated four to ten C−C bond distances away from the carbonyl functional group in the substrate. The site‐selectivity of the chlorination protocol was further exemplified by the installing of the C−Cl bond at the distal position of one example containing two tertiary carbon centers and the late‐stage functionalization of two drug molecules.