A. Stephen K. Hashmi

Innovative pretreatment, efficient catalysis, and intensified purification were implemented to develop continuous glycolysis for PET from post-consumer blended textile waste.

A copper‐catalyzed conversion of polyfluoroaryl chlorides to the corresponding phenols was developed. A simple ligand system was applied, as well as potassium carbonate as an inexpensive and effective base, while significantly suppressing competing S _N Ar pathways. The generality of the method was further demonstrated with simple aryl chlorides, which also underwent efficient hydroxylation. Mechanistic studies suggest that the reaction proceeds via a Cu(I)/Cu(III) catalytic cycle. Notably, the use of a sulfolane/water solvent system enabled high reactivity at a low catalyst loading, underscoring the practicality and scalability of this protocol.

In this article, we demonstrate the synthesis of 3‐substituted isoindoline monophosphine ligands by nucleophilic addition of Grignard reagents to peri ‐functionalized phosphine isoindolium salts. The bulky, α ‐branched isoindoline ligands were metalated using (dimethylsulfide)gold(I)chloride to obtain the phosphine gold(I)chloride complexes with a ligand conformation which is comparable to Buchwald biarylphosphine ligands induced by steric strain. In gold‐catalyzed reactions, the gold complexes show high catalytic activity at low catalyst loadings, outcompeting the established catalytic systems (Ph ₃ P)AuCl and (XPhos)AuCl.

In previous studies, para-dithieno- and diselenopyrazines were synthesized via nucleophilic hydrochalcogenation. However, the analogous oxygen-containing derivatives could not be obtained using this strategy. Herein, we report the synthesis of novel para-difuropyrazines employing a palladium-catalyzed methodology. These compounds exhibit high photoluminescence quantum yields of up to 91%, highlighting their potential for application in organic optoelectronic devices.

π-Extended dipyrrolopyrazines were synthesized via gold catalysis. Besides strong luminescence, these compounds exhibit interesting thin-film-properties.

The gold-catalyzed regioselective remote B(9)-H functionalization of o-carboranes through regioselective insertion of α-furyl silyl gold carbenes generated from silylenynones into the B(9)-H bond of o-carboranes offers facile and atom-economical access to various B(9)-α-furylsilyl-o-carboranes in moderate to good yields (up to 88%) with excellent regioselectivities. This method can also be expanded to the selective B-H functionalization of m-carboranes. The synthetic potential of this methodology is exemplified by gram-scale experiments and synthetic transformations of the products.

The rapid growth of polyethylene terephthalate (PET) waste and the limitations of conventional recycling methods for mixed waste streams emphasize the need for chemical recycling routes that deliver high-value monomers in a sustainable, resource-efficient manner. This work explores N-heterocyclic carbenes (NHCs) as organocatalysts for the glycolysis of PET with ethylene glycol to bis(hydroxyethyl)terephthalate (BHET), aiming for milder conditions and higher activity. A systematic catalyst screening links steric and electronic properties (percent buried volume, Tolman electronic parameter) of the NHCs to performance in the glycolysis process, resulting in a catalyst system with high PET conversion (up to 97%) and BHET yield (up to 65%). Mechanistic investigations (experimental and computational) support an anionic activation pathway for glycolysis. To lower the reaction temperature, selective cosolvent systems were explored, albeit with some loss of catalytic activity. Cooperative catalysis combining NHCs with Lewis acids enhances activity, leading to a high conversion (up to 90%) while maintaining lower temperatures than state-of-the-art glycolysis methods. The process was successfully transferred to post-consumer waste streams to validate the practicality.

Ring-opening copolymerization of CO ₂ with BnGE and/or CHO promoted by an Al/Fe/Co complex or BEt ₃ , combined with PPNCl, afforded PBnGEC and P(BnGEC- co -CHC). TBD-depolymerization of PBnGEC, PCHC and P(BnGEC- co -CHC) returned both corresponding cyclic carbonates.

Doyle–Kirmse rearrangement reactions are widely recognized as versatile and powerful synthetic tools, promoting the simultaneous generation of C─C and C─S bonds. While notable progress has been attained, Doyle–Kirmse rearrangement reactions involving cyanocarbenes have rarely been reported owing to the limited strategies available for the preparation of cyanocarbene precursors and its inherently restricted reactivity. Herein, we report photochemical Doyle–Kirmse rearrangement reactions of alkynyl triazenes via intermediate cyanocarbenes under metal‐ and additive‐free conditions, leading to valuable α‐mercapto‐nitriles in generally moderate‐to‐good yields. In contrast to existing methods that utilize alternative cyanocarbene precurors, this approach delivers the possibility to access highly substituted stereogenic carbon centers and it offers a safer alternative by avoiding hazardous reagents. The reactions proceed under mild conditions, and demonstrate broad substrate compatibility. In addition, upscaling of the reaction was successfully demonstrated. Besides the use of allylsulfides, propargyl as well as allenylsulfides were also feasible substrates demonstrating the great synthetic potential of the transformation.

Post-consumer blended textiles are utilised through selective PET glycolysis and upcycling of the cellulose-rich residue into reprocessable sulfur composites with enhanced mechanical properties. Image partly generated using Microsoft Copilot (Enterprise).