Robby Vroemans

Nature Synthesis, Published online: 03 April 2025; doi:10.1038/s44160-025-00782-y

The design of active sites in single-atom photocatalysts has a large impact on the catalytic reactivity. Here single-atom Pd–O catalytic sites are engineered by regulating their coordination environments. The Pd–O3 sites exhibit enhanced activity and selectivity for photocatalytic oxidation of toluene to benzaldehyde.

Incorporating fluorine into aliphatic rings induces significant changes in molecular conformation, acidity/basicity, and lipophilicity. A general method has been developed to transform exocyclic alkenes into saturated F₂-rings. This reaction utilizes the reagent C₆F₅I(OAc)₂, enabling the straightforward synthesis of gem-difluorinated macrocyclic, fused, spiro, bridged, and natural product-derived structures. The practicality of this protocol is demonstrated through several decagram-scale syntheses.

Abstract

A general method to convert simple exocyclic alkenes into saturated F₂-rings has been developed. The reaction involves reagent C₆F₅I(OAc)₂. The reaction efficiently works on the mg-, g-, and even multigram scale.

Nature Communications, Published online: 03 April 2025; doi:10.1038/s41467-025-58241-3

Here, the authors describe an N-heterocyclic carbene and chiral phosphoric acid dual-catalytic process for the desymmetrization of 1,3-diols, to achieve macrocyclization and stereoselective control over two chiral elements.

Nature Synthesis, Published online: 02 April 2025; doi:10.1038/s44160-025-00796-6

An organophotoreductant for Z-alkene synthesis

Nature, Published online: 31 March 2025; doi:10.1038/d41586-025-01012-3

Two experiments show that small payments can speed up peer review, but there might be unintended consequences. Plus, US grant cuts are ending scientific careers and Lyft drivers’ data reveals speeding-ticket racism.

Nature Communications, Published online: 01 April 2025; doi:10.1038/s41467-025-58278-4

Hypoglycemia is a serious and potentially life-threatening condition for people with insulin dependent diabetes, but preventative hypoglycemia therapies are elusive. Here, the authors report the use of catechol and boronic acid chemistry to design a self-crosslinkable hydrogel-based microneedle patch that delivers Zinc-Glucagon at low glucose levels and prevents insulin-induced hypoglycemia.

Abstract

A photoinduced energy transfer strategy has been developed for the direct 1,2-thiocyanato-imination of alkenes using N-SCN reagents. The methodology facilitates the synthesis of β-aminothiocyanates through N−S bond cleavage, with over 30 examples exhibiting yields up to 88%. Mechanistic studies reveal a radical pathway involving the generation of thiocyanate and iminyl radical species. The resulting β-aminothiocyanate serves as valuable building blocks for diverse transformations, particularly in the construction of SCN-containing bioactive molecules with potential pharmaceutical applications.

Nature, Published online: 19 March 2025; doi:10.1038/d41586-025-00742-8

Clean-energy research might be booming in Asia, but the energy transition has an uncertain future.

The impact of the solvent, the time, and the type of substrate on the evaluation of the antioxidant activity (AoA) of lignin via the DPPH assay was investigated in this work. This allowed us to provide guidelines on how to perform the DPPH assay for a more reliable evaluation of lignin AoA.

Abstract

The most widespread procedure to measure the antioxidant activity of lignin is via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. So far, different experimental procedures (i. e., different solvent, time, etc.) have been used to implement the DPPH methodology without estimating the effect of such modifications on the experimental procedure. To overcome this issue, the impact of the solvent, the time, and the type of substrate on the evaluation of the antioxidant activity (AoA) of lignin via the DPPH assay was investigated in this work. We found that multiple different parameters affect the evaluation of the AoA of lignin: i) the stability of the DPPH radical and the lignin solubility in a given solvent; ii) the importance of reaching steady state (the effect of time); iii) the background noise associated with lignin absorbance at λ=515 nm (used to monitor the DPPH radical scavenging); iv) lignin structure; v) providing a normalized radical scavenging index (nRSI); vi) comparing nRSI vs. inhibition percentage (IP) values. Overall, our investigation allowed us to provide guidelines on how to perform the DPPH assay for a more reliable evaluation of lignin AoA.

Editor-in-Chief Charlotte Gers-Panther together with Frank Maaß and Nathalie Weickgenannt, Editors-in-Chief of Angewandte Chemie, introduce the new journal Angewandte Chemie Novit — a space for exceptional research in all significant and emerging areas of chemistry.

Triphenylphosphine-free Rh catalysts are the preferred catalyst type for the regioselective hydroformylation of methyl 4-chlorocinnamate to the pharmaceutically interesting racemic β-aldehyde. High regioselectivities of 88–93 % to the β-aldehyde were obtained with various phosphine ligand-free rhodium complexes. In contrast, adding triphenylphosphine as common phosphine ligand shifts the regioselectivity to the undesired α-aldehyde.

Abstract

Hydroformylation of α,β-unsaturated esters is an atom-economical route towards aldehydes as precursors for pharmaceuticals. In this work, regioselective hydroformylation of an α,β-unsaturated ester to the β-aldehyde was initially re-evaluated using a commercial Rh catalyst sample named “[HRh(PPh₃)₄]” due to reported high selectivity for the β-aldehyde with this type of catalyst. However, while such high selectivity was achieved, subsequent investigation of this sample by high-pressure NMR and in situ IR spectroscopy under process conditions revealed a behavior like a phosphine-free system, indicating that the sample is decomposed and may be present as rhodium carbonyl clusters. This hypothesis has been supported by hydroformylation experiments with and without phosphine ligands. While a strong decrease in regioselectivity to the β-aldehyde was observed in the presence of triphenylphosphine as added ligand, phosphine-free rhodium complexes led to high regioselectivities. In detail, the hydroformylation showed high regioselectivity (91 %) and overall selectivity to the β-aldehyde (70–77 %) with [Rh₆(CO)₁₆] as well as [Rh(acac)(CO)₂] as ligand-free rhodium complexes. With further unmodified, phosphine-free rhodium compounds as catalysts, again high regioselectivities (90–93 %) towards the β-aldehyde were obtained. Thus, our results indicate that non-modified triphenylphosphine-free Rh catalysts are efficient catalysts for regioselective hydroformylation of β-aryl-substituted α,β-unsaturated carboxylates to the β-aldehyde.

Journal of Porphyrins and Phthalocyanines, Volume 29, Issue 01n02, Page 276-279, January & February 2025.
A mild and efficient method for the acid-promoted demetallation of functionalized metalloporphyrins is described. In contrast to the normally harsh conditions required, a variety of Cu porphyrins were rapidly demetallated in excellent yields using methanesulfonic acid in a chlorinated hydrocarbon solvent at room temperature or under microwave heating. Some Co, Ni, and Ag porphyrins could also be efficiently demetallated. Notably, the presence of a small amount of a coordinating solvent in the reaction mixture either completely inhibited the demetallation or significantly slowed it down. Electron withdrawing functionality also slowed down the demetallation time.

Recent advances in photochemical reactions are highlighted in this review, focusing on the reaction carried out without using any transition metal catalysts or organic photosensitizers. The aim of this review is to emphasize the chemical properties of the reactants or reaction intermediates that enable them to harness photon energy to initiate chemical reactions.

Abstract

Photosynthesis in plants has inspired photochemical reactions in organic chemistry. Synthetic organic chemists always seek cost-effective, operationally simple, averting the use of toxic and difficult-to-remove metallic catalysts, atom economical, and high product purity in organic reactions. In the last few decades, the use of light as a catalyst in organic reactions has increased exponentially as literature has exploded with examples, particularly by using toxic and expensive metal complexes, photosensitizers like organic dyes, hypervalent iodine, or by using inorganic semiconductors. In this report, we have selected a few interesting examples of photochemical reactions performed without using any metallic catalyst or photosensitizers. These examples use the inherent potential of reactants to utilize light energy to initiate chemical reactions. Our main emphasis is to highlight the structural features in the reactants that can absorb light energy or form an electron donor-acceptor (EDA) complex during the reaction to initiate the photochemical reaction. Considering the high degree of variability in the photochemical reactions, the utmost care has been taken to present the most accurate reaction conditions. A short introductory section on photochemical reactions will act as an anchor that will revolve around the examples discussed and explain the underlying principle of the photochemical reaction mechanism.

We report that an air-stable “naked nickel”, Ni(^4-CF3stb)₃, can efficiently catalyze heteroaryl–heteroaryl Suzuki–Miyaura cross-coupling (SMC) reactions in the absence of exogenous ligands. This protocol permits the construction of >15 different heterobiaryls containing multiple Lewis basic heteroatoms from a broad set of 6-membered heteroaryl bromides with 5- and 6-membered heterocyclic B-nucleophiles.

Abstract

In this article, we report that the air-stable “naked nickel”, [Ni(^4-CF3stb)₃], is a competent catalyst in the catalytic Suzuki–Miyaura cross-coupling reaction (SMC) between heteroaryl bromides and heteroaromatic boron-based nucleophiles. The catalytic system is characterized by its ability to avoid decomposition or deactivation in the presence of multiple Lewis basic sites. The protocol permits the formation of C‒C bonds between two heteroaryl moieties in the absence of complex exogenous ligands, thus minimizing screening procedures and simplifying reaction setups. This method accommodates combinations of distinct 6-membered heteroaryl bromides and 5- and 6-membered heterocyclic B-based nucleophiles.

Molecules with large gaps between their first singlet and triplet excited states (ΔEST) are key components of various modern technologies, most prominently singlet fission photovoltaics and triplet-triplet annihilation upconversion. The design of these molecules is hampered by the fact that only limited rules for maximizing ΔEST exist, other than increasing the overlap between the frontier molecular orbitals (FMO). Here we suggest a new strategy for tuning and maximizing ΔEST based on a detailed analysis of the underlying quantum mechanical energy terms. We present a model based on the transition density and derive three straightforward design rules: ΔEST values can be maximized by (i) minimizing the overall number of π-electrons, (ii) reducing delocalization, and (iii) optimizing specific geometric interactions. The validity of these rules is first exemplified for a set of 18 hydrocarbon backbones before proceeding to a varied set of dye molecules highlighting their transferability to realistic settings. We believe that the developed rules will provide an enormous boost to the field enabling rational design instead of trial-and-error screening. More generally, this work demonstrates the power of going beyond the FMO approximation in designing advanced molecular materials.