Robby Vroemans

Publication date: Available online 1 June 2026

Source: Trends in Chemistry

Author(s): Vishal Jyoti Roy, Nishan Khanal, Dennis Chung-Yang Huang

The depolymerization of polyurethane foams strongly depends on carbonate structure. Aryl carbonates improve hard-segment solubility but generate side products. Alkyl carbonates give cleaner products yet suffer from limited hard-block solubility and require anisole as a cosolvent. Mixed carbonate systems balance these effects, improving solubility while reducing side products. The methyl carbonate system also shows favorable phase separation, facilitating product work-up.

Chemical recycling of polyurethane foams (PUFs) remains challenging due to their crosslinked structure. Depolymerization with organic carbonates offers a phosgene-free route to recover both polyols and aromatic monomers through carbonate-mediated carbonyl exchange. Here, we evaluate the reactivity of a series of carbonates, including dimethyl carbonate (DMC), diphenyl carbonate (DPC), methyl phenyl carbonate (MPC), and mixed DMC/DPC, in the depolymerization of TDI-based flexible PUF (190°C, 4 h, with Zn(OAc)₂ as a catalyst). DPC promotes equilibration between urea and carbamate species but generates side products resulting in lower selectivity. MPC behaves similarly to the DMC/DPC mixture, resulting in the formation of mixed carbamate species, thus confirming carbonyl exchange as the underlying mechanism. In contrast, DMC yields cleaner products but suffers from limited dissolution of the aromatic hard blocks at lower temperatures. Using anisole as a cosolvent resolves this limitation, enhancing the accessibility of the hard domains, resulting in the recovery of 85% of methyl-functionalized toluene dicarbamate (Me-TDC) and of 95% of the polyol. Additionally, DMC also allows easy product separation. Overall, this study clarifies how carbonate structure affects depolymerization pathways, side-product formation, and hard-domain accessibility providing selective and phosgene-free chemical recycling strategies for PUFs.

In this review, we highlight recent advances in the synthesis and reactivity of 1,1-diborylalkenes and 1,2-diborylalkenes, along with various transformations leading to C-C, C-heteroatom, and multicomponent products. By providing a comprehensive and practical resource, this review aims to assist researchers in exploring the synthetic utility of 1,1 and 1,2-alkenyl bis(boronate) compounds.

In this review, we highlight recent advances in the synthesis and reactivity of 1,1-diborylalkenes and 1,2-diborylalkenes, along with various transformations leading to CC, C-heteroatom, and multicomponent products. The study covers both symmetrical and unsymmetrical strategies for synthesizing bis(boronates) from alkenes, alkynes, and carbonyl precursors, including metal-catalyzed, base-promoted, and organophosphorus-mediated methods. In addition to demonstrating their versatility in building complex molecular frameworks for medicinal chemistry, alkenyl bis(boronates) are used in regioselective transformations. By providing a comprehensive and practical resource, this review aims to assist researchers in exploring the synthetic utility of 1,1 and 1,2-alkenyl bis(boronate) compounds.

This review highlights recent advances in transition-metal-catalyzed interrupted borrowing hydrogen reactions with methanol as a versatile methylene donor, and emphasizes their transformative potential in sustainable methanol chemistry.

ABSTRACT

The interrupted borrowing hydrogen (IBH) strategy enables the selective interruption of the complete “dehydrogenation-transformation-hydrogenation” process of traditional hydrogen borrowing (BH) reactions via catalytic cycle modulation, thereby facilitating the efficient synthesis of high-value-added chemicals inaccessible by conventional methods. This process exhibits excellent atomic economy and step economy, affording only water and hydrogen as by-products, thereby demonstrating remarkable green and sustainable features. As an abundant, green, and sustainable C1 source, methanol-mediated IBH reactions have emerged as a prominent research hotspot in organic synthesis and catalysis in recent years. This review comprehensively summarizes recent advances in IBH reactions for the preparation of various organic synthetic building blocks via C─C, C─O, C─N, C─P bond formation reactions using methanol as a methylene bridging reagent under transition metal catalysis.

This review highlights the recent progress made in the field of 3D printing of porphyrin derivatives. 3D printing of porphyrins is performed using various techniques, such as fused deposition modeling (FDM), inkjet printing (IJP), direct ink writing (DIW), and stereolithography (SLA). The printed materials are used as sensors, tissue engineering materials, and electrocatalysts, etc.

ABSTRACT

3D printing has transformed academia and industry by providing rapid prototyping, enhanced durability, and customized manufacturing solutions. It creates complex objects in layer by layer (i.e., additive manufacturing) from computer-aided designs (CAD). Although 3D printing has been widely used for producing machine parts, devices, etc., its application in synthetic chemistry and nanomaterials is still in its early stages. Porphyrins are class of naturally occurring macrocycle that play key roles in biological processes such as photosynthesis, oxygen transport, etc. Additionally, synthetic porphyrins and their derivatives, prepared using established methods, are now being integrated into advanced materials, including metal-organic frameworks (MOFs), 2D materials, and nanomaterials. This mini-review portraits the reports of converting porphyrins into 3D printable inks, illustrating how the fusion of porphyrin chemistry and 3D printing technology can yield significant breakthroughs. We present examples of porphyrin derivatives that have been 3D printed using techniques such as fused deposition modeling (FDM), inkjet printing (IJP), direct ink writing (DIW), and stereolithography (SLA). This review examines the compatibility between 3D printing techniques and porphyrin chemistry and highlights the potential for translating laboratory-scale developments into industrial 3D printing of porphyrins, additive manufacturing, DIW printing, FDM printing, SLA printing applications.

Mechanochemistry is redefining metal catalysis by controlling catalyst formulation, speciation, and deployment. This Review shows how milling, LAG, RAM, and TSE enable rapid metal-complex assembly, distinctive catalytic manifolds, and scalable synthesis beyond solution chemistry.

ABSTRACT

Mechanochemistry and transition-metal catalysis are converging into a platform in which mechanical energy reshapes catalyst formulation, speciation, and operative state, rather than simply replacing solvent. Through intense mixing, continuously renewed interfaces, liquid-assisted grinding (LAG), and rheological control, milling can direct metal-complex assembly, activation, reactivity, and selectivity in ways difficult to reproduce in solution. These attributes streamline catalyst preparation, lessen dependence on stringent inert-atmosphere protocols, and open access to transformations that are inefficient, selective only under milling, or inaccessible by conventional methods. This Review examines the mechanochemical synthesis of transition-metal complexes and their direct deployment in catalytic organic transformations, from earth-abundant first-row metals to selected noble-metal systems. Quantitative benchmarks, including enantioselectivities up to 99% ee, turnover frequencies above 100 h⁻¹, and cross-electrophile couplings completed within minutes, demonstrate that mechanocatalysis can deliver not only greener variants of known reactions but also distinct reactivity regimes. Mechanistic uncertainty, reproducibility, and scalable technologies such as twin-screw extrusion (TSE) and resonant acoustic mixing (RAM) are assessed, framing mechanocatalysis as both an enabling methodology and a conceptual basis for next-generation green catalysis.

Visible-light-driven fluorination reactions have been widely developed in recent years. This review highlights recent advances in visible-light-mediated C–F bond formation, providing efficient strategies for the synthesis of a wide range of fluorinated compounds.

Fluorine is a widely used structural element in chemistry and has been utilized in diverse fields, including organic chemistry and pharmaceuticals. Fluorine's diverse applications have led to the development of numerous fluorination reaction methods. Visible-light-assisted reactions have attracted significant interest and development in organic chemistry due to their advantages in reaction conditions and efficiency. In particular, visible-light-driven fluorination has been recognized as a valuable synthetic strategy, resulting in the production of numerous fluorinated compounds. This review presents a summary of recent developments in visible-light-driven fluorination reactions developed since 2021.

Steric shielding over electronic deactivation: a congested diboron reagent ([OxB]₂) defies expectations, enabling direct catalytic synthesis of stable, deprotectable alkylborons.

This article reports the synthesis of the dimer of oxazaborolidinone (OxB), [OxB]₂, a sterically hindered protecting group for boron. This highly congested unique diboron reagent functions as an efficient borylation agent, enabling the direct synthesis of alkylboron compounds, which has been challenging with conventional methods. Remarkably, despite its significant steric bulk, [OxB]₂ undergoes smooth transmetalation with a copper catalyst. Through complementary reductive borylation and cross-coupling with alkyl halides, we successfully prepared a range of primary and secondary alkylboron compounds—traditionally unstable and difficult to access—as stable Alkyl-OxB derivatives. Furthermore, the resulting Alkyl-OxB derivatives can be readily deprotected under mild conditions to furnish the corresponding alkylboronic acids. Leveraging this property, we demonstrated the iterative Suzuki–Miyaura cross-coupling of protected alkylboron species, a transformation that has remained elusive to date.

We report novel trans-L monohydrido ^iPrRu-MACHO derivatives as precatalysts operating under mild conditions with high activity and selectivity. Their performance in CO₂ hydrogenation, formic acid dehydrogenation, and levulinic acid hydrogenation was evaluated and compared to the commercial ^iPrRu-MACHO precursor, offering improved catalytic efficiency beyond traditional P-substituent modifications.

The Ru–MACHO complex acts as a precatalyst for a plethora of significant catalytic transformations. However, since its discovery approximately two decades ago, most enhancement attempts have been limited to varying the P-substituents for increasing catalyst performance or replacing Ru for greener alternatives. In this study we synthesize novel trans-L monohydrido ^iPrRu-MACHO complex derivatives that can act as precatalysts operating under mild conditions while maintaining high activity and selectivity in a variety of chemical transformations. Specifically, we deeply studied their potentially trans influence and investigated their catalytic efficiency for CO₂ hydrogenation, formic acid dehydrogenation, and levulinic acid hydrogenation, and we compared their activity with their commercially available precursor ( ^iPrRu-MACHO).

Light provides a noninvasive, exquisitely precise handle to control fluorescence. This review navigates the chemical ingenuity behind small-molecule fluorophores engineered to respond to light—tools that are reshaping bioimaging. We chart the evolution from simple caged dyes to sophisticated “AND-gate” systems, offering a roadmap of molecular design strategies that confer on-demand control over emission intensity, color, and location.

ABSTRACT

Photoresponsive fluorophores, which enable precise spatiotemporal control of emission through light irradiation, are fundamentally important for advanced bioimaging and sensing applications. This review comprehensively surveys contemporary chemical strategies for the rational design of such smart optical probes. We systematically categorize and discuss the underlying design principles of major classes of photoresponsive fluorophores, including photoactivatable, photo-deactivatable, photoconvertible, and dual-activatable systems—the latter requiring the simultaneous occurrence of a specific biochemical event and external photonic input to trigger fluorescence. Detailed examination is provided on the key chemical approaches employed in their engineering, encompassing the use of caging groups, cage-free molecular designs, directed photooxidation, electrocyclization reactions, and other phototriggered molecular rearrangements. By elucidating the intricate relationships between molecular structure and photophysical function, this overview underscores how innovative chemical design affords unprecedented spatiotemporal precision in fluorescence output, thereby expanding the toolbox for dynamic biological investigation and analytical detection.

Under elevated voltage (≥4.1 V) and trace moisture, silicone-based Kapton adhesives release trimethylsilyl species that react with acetamide to form trimethylsilyl acetamide (TMSA). This adhesive-triggered silylation pathway accelerates electrolyte degradation in commercial 18650 supercapacitors.

Silicone adhesives in polyimide (Kapton) tape are revealed as hidden initiators of electrolyte decomposition in commercial-scale supercapacitors employing acetonitrile-based electrolytes. This study uncovers a previously unrecognized, moisture-assisted silylation mechanism in which silicone-derived trimethylsilyl species react with acetamide, a hydrolysis product of acetonitrile, in the presence of triethylamine (TETA), forming trimethylsilyl acetamide (TMSA) via nucleophilic substitution. This degradation pathway, activated under elevated voltage (≥4.1 V) and trace moisture, is distinct from known electrode-induced processes and accelerates electrolyte breakdown. A suite of analytical techniques, including gas chromatography–mass spectrometry (GC–MS), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), and electrochemical testing, unambiguously identifies the silicone adhesive as the primary source of reactive silicon. Control experiments confirm that TMSA formation requires both silicone adhesives and water, validating the proposed mechanism. These findings challenge the conventional assumption that non-electroactive components are chemically inert and demonstrate that auxiliary materials can drive parasitic side reactions under realistic abuse conditions. This work highlights the critical importance of full-system material compatibility screening in supercapacitor design and provides mechanistic insight for enhancing device longevity and safety.

Nature Communications, Published online: 01 April 2026; doi:10.1038/s41467-026-71201-9

Bicyclo[3.3.1]nonane skeletons, widely found in natural products and bioactive molecules, hold great value in drug discovery. Transition-metal-catalyzed asymmetric synthesis offers an efficient approach to these frameworks. This review summarizes recent advances in Pd/Rh/Cu-catalyzed asymmetric cyclizations, discussing challenges and future directions.

ABSTRACT

The bicyclo[3.3.1]nonane ring skeletons, with their distinctive three-dimensional structural features, are widely found in natural products, bioactive molecules, and functional materials, demonstrating significant value particularly in drug discovery. However, their structural rigidity and ring strain pose formidable synthetic challenges, including lengthy synthetic routes, poor selectivity, and low atom economy in conventional approaches. In recent years, transition-metal-catalyzed asymmetric synthesis has emerged as a powerful strategy for constructing bicyclo[3.3.1]nonane frameworks, owing to its efficiency and high selectivity. This review focuses on advances in Pd/Rh/Cu catalyzed asymmetric cyclization strategies for such architectures, systematically summarizing the characteristics and challenges of various reaction types, while providing perspectives on future research directions.