Helvetica Chimica Acta最新文献

To appreciate 10 years of cell-penetrating poly(disulfide)s (CPDs), this review comprehensively covers the structures realized by now. CPDs have been introduced as dynamic covalent polymers that i) are obtained from cyclic disulfide monomers by ring-opening polymerization (ROP) and ii) enter cells by thiol-mediated uptake. They were discovered in 2014 and have been used since then for diverse delivery applications in vitro and in vivo. The introduction briefly sketches their mode of action, as far as it is known. The main part lists the CPDs realized so far, organized by their structures, with selected examples for biological applications. The final chapters cover the few cyclic monomers other than lipoic acid derivatives that have been explored and links to related topics such as templated ROP of cyclic disulfides in lipoplexes and liposomes and related delivery motifs. We hope this review offers a solid and productive basis for future progress with CPD research and its use in science and society.

Colloidal III–V arsenide quantum dots (QDs) are promising low-toxicity, solution-processable materials for near-infrared optoelectronics, yet their development has been constrained by the scarcity of suitable precursors and proneness to oxidation. Existing routes either rely on highly reactive but toxic, pyrophoric group-14-substituted arsines, or on safer aminoarsines that require in situ reduction and cause staggered rather than a single burst nucleation. We introduce aluminum tris[bis(mesitoyl)arsenide] as a nonpyrophoric and air-stable precursor that, upon nucleophilic attack, directly delivers the formally As³⁻ species. Using this precursor, we synthesized 2.3–4.6 nm large InAs QDs and 2–5.5 nm large Cd₃As₂ QDs with photoluminescence tunable in the 800–2250 nm range. These results establish aluminum tris[bis(mesitoyl)arsenide] as a versatile precursor, enabling safe and controlled syntheses of various arsenide QDs.

In pseudo-natural product (PNP) design, natural product fragments are combined in arrangements not found in nature to afford novel biologically relevant NP-related compound classes. A pseudo-natural product compound collection inspired by aspidospermidine-, strychnos-, and koumine monoterpene alkaloids was designed and rapidly synthesized to afford a collection of 78 compounds representing eight structurally different PNP classes. Evaluation of the collection for biological relevance by means of the cell painting assay, including a recently reported subprofile analysis, revealed that one of the structural classes is enriched in and defines a new chemotype of de novo pyrimidine biosynthesis inhibitors. Our results exemplify the combination of pseudo-natural product design and unbiased morphological screening technologies as an efficient means to rapidly access and identify novel biologically relevant chemotypes.

Ortho-alkoxy trifluoroacetophenones undergo efficient cyclization to benzofuranols under UV light irradiation (370 nm). Key to success is a 1,6-hydrogen atom transfer (1,6-HAT), which is enabled by the unique properties of the trifluoroacetophenone unit and strategic positioning of the methoxy group. The reaction proceeds best under dilute conditions, in polar aprotic solvents, and with high-intensity irradiation. Although triplet quenching and intermolecular HAT limit certain aromatic substitution patterns, the reaction still accommodates a diverse set of substrates, providing access to tertiary benzofuranols, including spirocyclic compounds (12 examples, up to 92% yield, up to 90:10 diastereomeric ratios [dr]). Subsequent dehydration provides trifluoromethyl-substituted benzofurans, offering a convenient route to these heterocycles.

This study describes the applications of molybdenum-catalyzed homogeneous cross-metathesis approaches, which led to the production of the unique macrocyclic musk lactone Ambrettolide under essentially solvent free conditions. Renewable octenyl decenoate 16 was pretreated to remove traces of water, oxygen, and peroxides and polymerized at low catalyst loadings to control the rate of ethylene evolution. In a subsequent intramolecular transesterification-based depolymerization step, a new quality of Ambrettolide was obtained with an E/Z ratio of 85/15 and desired organoleptic properties, now available as AmbreXolide™.

Bis(pyridylimino) isoindolides (BPIs) are important redox non-innocent ligands in coordination chemistry and homogeneous catalysis. BPIs can be doubly reduced allowing a change between the mono-, di- and trianionic state. In this article, the first isolation of a monomeric compound with radical dianionic BPI ligand is reported, realized as potassium complex with supporting crown ether ligands. Single-crystal X-ray diffraction (SC-XRD) revealed an η⁵-coordination of the five-membered isoindolide ring, which is so far unprecedented in BPI chemistry. The radical was investigated by electron paramagnetic resonance (EPR) spectroscopy. Structures of the pincer-type rotamers of BPI in the mono-, di- and trianionic state were calculated by density functional theory (DFT) methods to benchmark the BPI bond lengths theoretically upon varied redox states. Bond lengths within the herein described BPI radical deviate significantly from the free BPI dianion, depicting how careful structure-redox-state correlations must be drawn in the coordination chemistry of redox-active BPIs.

Mechanochemistry can mediate reactions containing components that are poorly soluble in organic solvents, thereby facilitating access to new chemical space. These reagents may also be safer to handle and less costly than analogs used in solution-state reactions, providing secondary tangible benefits. In this study, we report the use of sodium ascorbate as a sacrificial reductant in net reductive pinacol couplings of aromatic aldehydes and ketones driven by mechanophotocatalysis. Sodium ascorbate replaces the sacrificial reductants typically used to deliver these 1,2-diol products (such as DIPEA and the Hantzsch ester). The solvent-minimized protocol returned more consistent results than the solution-state reference reaction, highlighting mechanophotocatalysis as a valuable tool for mediating heterogeneous photochemical reactions. An initial positive result for a reductive amination protocol using ascorbate is also disclosed.

In heterogeneous catalysis, metal oxides are an important group of materials used to support nanoparticle catalysts. These metal oxides, however, are not completely inert and interact with the (transition-) metal nanoparticle, potentially influencing the overall catalytic properties of the catalyst. This study investigates the influence of the metal oxide support on the catalytic properties of cobalt-based CO₂ hydrogenation catalysts. A series of cobalt nanoparticles supported on Al₂O₃, SiO₂, CeO₂, ZrO₂, and TiO₂ was synthesized using a standardized surface organometallic chemistry approach to provide comparability and characterized by standard microscopy and spectroscopic methods. Catalytic evaluation in CO₂ hydrogenation identifies SiO₂ as a unique support in promoting reverse water–gas shift reactivity in cobalt, while other supports yielded methanation reactivity as commonly observed for cobalt-based CO₂ hydrogenation. Notably, doping supports with Si, here Al₂O₃ and TiO₂, is enough to shift the reactivity of Co toward RWGS, paralleling what is observed when Co is supported on SiO₂.

Copper-catalyzed S_N2' substitution reactions of chiral propargyl compounds provides an efficient synthetic method for chiral allenes that have widespread applications in pharmaceuticals and artificial functional materials. However, compared with the S_N2' reaction catalyzed by palladium, ruthenium, and other noble metals, the development of S_N2' reaction catalyzed by copper is relatively delayed due to its sensitivity to steric hindrance. Herein we reported a highly selective copper-catalyzed S_N2' substitution reaction through the use of weakly nucleophilic zinc reagents. A wide variety of polyfluoroaryl allenes bearing an assortment of functional groups (36 examples) are compatible with this catalysis system. It is worth noting that chiral polyfluoroaryl allenes can also be efficiently constructed from chiral propargyl esters via this S_N2' reaction. A series of mechanism verification experiments and DFT calculations also provide a basis for the reaction mechanism and the stereo-model of chiral transfer. Moreover, the preparation of other valuable polyfluoroarene containing compounds from polyfluoroaryl allenes also proves the synthetic utility of this methodology.

I chose chemistry because it is fundamental to our world. Chemistry influences nearly every facet of our existence. Also, assembling molecules is like playing with LEGO which is awesome. The secret of being a successful scientist is being curious, passionate and never stop trying. My favorite quote in French is “La vie est dure, mais pas la mienne,” which can be translated to “Life is hard, but not mine.”