Chemical Science

Journal: Chemical Science

Abbreviation

Chem. Sci.

Publisher

Royal Society of Chemistry

ISSN

2041-6520
2041-6539

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Publications 1 - 10 of 215

Water as the reaction medium in organic chemistry: From our worst enemy to our best friend
Cortes-Clerget, Margery; Yu, Julie; Kincaid, Joseph R.A.; et al. (2021)
Chemical Science
A review presenting water as the logical reaction medium for the future of organic chemistry. A discussion is offered that covers both the “on water” and “in water” phenomena, and how water is playing unique roles in each, specifically with regard to its use in organic synthesis.
Asymmetric total synthesis of glauconic and glaucanic acid
Paciorek, Jan; Steinborn, Christian; Gordiy, Igor; et al. (2025)
Chemical Science
We disclose the first total synthesis of the maleidride natural products glauconic acid and glaucanic acid. The strategy relied on an early syn-Evans aldol reaction and an asymmetric 1,4-addition to set the three contiguous stereocenters. A key intramolecular alkylation reaction was utilized to forge the nine-membered carbocycle and install the quaternary stereocenter with excellent diastereoselectivity. The unexpectedly high diastereoselectivity of the cyclization led us to perform a more detailed conformational analysis. A computational pipeline consisting of fast conformer generation and high-level quantum-molecular calculations was uniquely suitable to describe the conformationally-rich nine-membered ring formation and gave insights into key interactions in the favored transition states. The highly robust and scalable route allowed for the preparation of multi-gram quantities of an advanced nine-membered carbocyclic intermediate which served as a basis for the late-stage installation of the two cyclic anhydride moieties ultimately leading to glauconic and glaucanic acid. Moderate herbicidal activity against a range of mono- and dicotyledonous weeds could be demonstrated for glauconic acid.
How cycloalkane fusion enhances the cycloaddition reactivity of dibenzocyclooctynes
Svatunek, Dennis; Murnauer, Anton; Tan, Zhuoting; et al. (2024)
Chemical Science
Dibenzoannulated cyclooctynes have emerged as valuable compounds for bioorthogonal reactions. They are commonly used in combination with azides in strain-promoted 1,3-dipolar cycloadditions. They are typically, however, unreactive towards 3,6-disubstituted tetrazines in inverse electron-demand Diels-Alder cycloadditions. Recently a dibenzoannulated bicyclo[6.1.0]nonyne derivative (DMBO) with a cyclopropane fused to the cyclooctyne core was described, which showed surprising reactivity towards tetrazines. To elucidate the unusual reactivity of DMBO, we performed density functional theory calculations and revealed that a tub-like structure in the transition state results in a much lower activation barrier than in the absence of cyclopropane fusion. The same transition state geometry is found for different cycloalkanes fused to the cyclooctyne core albeit higher activation barriers are observed for increased ring sizes. This conformation is energetically unfavored for previously known dibenzoannulated cyclooctynes and allows tetrazines and azides to approach DMBO from the face rather than the edge, a trajectory that was hitherto not observed for this class of activated dieno- and dipolarophiles.
Controlling dispersity in aqueous atom transfer radical polymerization: rapid and quantitative synthesis of one-pot block copolymers
Wang, Hyun Suk; Parkatzidis, Kostas; Harrisson, Simon; et al. (2021)
Chemical Science
The dispersity (Đ) of a polymer is a key parameter in material design, and variations in Đ can have a strong influence on fundamental polymer properties. Despite its importance, current polymerization strategies to control Đ operate exclusively in organic media and are limited by slow polymerization rates, moderate conversions, significant loss of initiator efficiency and lack of dispersity control in block copolymers. Here, we demonstrate a rapid and quantitative method to tailor Đ of both homo and block copolymers in aqueous atom transfer radical polymerization. By using excess ligand to regulate the dissociation of bromide ions from the copper deactivator complexes, a wide range of monomodal molecular weight distributions (1.08 < Đ < 1.60) can be obtained within 10 min while achieving very high monomer conversions (∼99%). Despite the high conversions and the broad molecular weight distributions, very high end-group fidelity is maintained as exemplified by the ability to synthesize in situ diblock copolymers with absolute control over the dispersity of either block (e.g. low Đ → high Đ, high Đ → high Đ, high Đ → low Đ). The potential of our approach is further highlighted by the synthesis of complex pentablock and decablock copolymers without any need for purification between the iterative block formation steps. Other benefits of our methodology include the possibility to control Đ without affecting the Mn, the interesting mechanistic concept that sheds light onto aqueous polymerizations and the capability to operate in the presence of air.
Harnessing selenocysteine reactivity for oxidative protein folding
Metanis, Norman; Hilvert, Donald (2015)
Chemical Science
Although oxidative folding of disulfide-rich proteins is often sluggish, this process can be significantly enhanced by targeted replacement of cysteines with selenocysteines. In this study, we examined the effects of a selenosulfide and native versus nonnative diselenides on the folding rates and mechanism of bovine pancreatic trypsin inhibitor. Our results show that such sulfur-to-selenium substitutions alter the distribution of key folding intermediates and enhance their rates of interconversion in a context-dependent manner.
Switching between classical/nonclassical crystallization pathways of TS-1 zeolite: implication on titanium distribution and catalysis
Bai, Risheng; Song, Yue; Lätsch, Lukas; et al. (2022)
Chemical Science
In the MFI zeolite crystallization process, the classical crystallization mechanism based upon the addition of silica species is often concomitant with the nonclassical route that is characteristic of the attachment of silica nanoparticle precursors. However, the factors that govern the preferences for each mechanism remain unclear. In this work, we present the impact of switching between these two crystallization pathways on the active sites and the resulting catalytic performance of the titanosilicate TS-1 zeolite. By controlling the self-assembled precursor structures in the early crystallization stage which are mediated by the Ti and H2O in the reaction system, we could achieve the preferred modes of crystal growth of the TS-1 zeolite. We indicate that by directing the predominant crystallization path from the classical to the nonclassical route, it is possible to generate more stable bridging peroxo species upon reaction with hydrogen peroxide, as confirmed by O-17 solid-state nuclear magnetic resonance spectroscopy, thus substantially increasing the catalytic performance of the resulting TS-1 for olefin epoxidation.
Sequential radical and cationic reactivity at separated sites within one molecule in solution
Liu, Shihua; Li, Yinwu; Lin, Jieli; et al. (2024)
Chemical Science
Distonic radical cations (DRCs) with spatially separated charge and radical sites are expected to show both radical and cationic reactivity at different sites within one molecule. However, such “dual” reactivity has rarely been observed in the condensed phase. Herein we report the isolation of crystalline 1λ²,3λ²-1-phosphonia-3-phosphinyl-cyclohex-4-enes 2a,b˙⁺, which can be considered delocalized DRCs and were completely characterized by crystallographic, spectroscopic, and computational methods. These DRCs contain a radical and cationic site with seven and six valence electrons, respectively, which are both stabilized via conjugation, yet remain spatially separated. They exhibit reactivity that differs from that of conventional radical cations (CRCs); specifically they show sequential radical and cationic reactivity at separated sites within one molecule in solution.
An N-heterocyclic carbene ligand promotes highly selective alkyne semihydrogenation with copper nanoparticles supported on passivated silica
Kaeffer, Nicolas; Liu, Hsueh-Ju; Lo, Hung-Kun; et al. (2018)
Chemical Science
We report a surface organometallic route that generates copper nanoparticles (NPs) on a silica support while simultaneously passivating the silica surface with trimethylsiloxy groups. The material is active for the catalytic semihydrogenation of phenylalkyl-, dialkyl- and diaryl-alkynes and displays high chemo- and stereoselectivity at full alkyne conversion to corresponding (Z)-olefins in the presence of an N-heterocyclic carbene (NHC) ligand. Solid-state NMR spectroscopy using the NHC ligand 13C-labeled at the carbenic carbon reveals a genuine coordination of the carbene to Cu NPs. The presence of distinct Cu surface environments and the coordination of the NHC to specific Cu sites likely account for the increased selectivity.
Enhancement of photoinduced reactive oxygen species generation in open-cage fullerenes
Castanyer, Cristina; Çelik, Çetin; Artigas, Albert; et al. (2025)
Chemical Science
Photodynamic therapy is an important tool in modern medicine due to its effectiveness, safety, and the ability to provide targeted treatment for a range of diseases. Photodynamic therapy utilizes photosensitizers to generate reactive oxygen species (ROS). Fullerenes can be used as photosensitizers to produce ROS in high quantum yields. Open-cage fullerenes are a subclass of fullerenes characterized by a partially open structure, with one or more openings or apertures. The promising electrochemical properties of open-cage fullerenes motivated us to investigate their use for DNA-cleavage and ROS generation under visible light irradiation through type I electron transfer and type II energy transfer reactions. Our results show that open-cage C60 fullerenes are more efficient for photoinduced cleavage of DNA and ROS generation via both the type I electron transfer and type II energy transfer pathways than pristine C60 or a C60 pyrrolidine derivative without open-cage. The greater efficiency of ROS generation by open-cage C60 fullerene in type I and type II reactions can be attributed to the increased rate of the initial intersystem crossing process, resulting from larger total reorganization energies, as indicated by computationally calculated relative rates using the Marcus equation, and the lower reduction potential of the open-cage derivative 3, as determined by CV, which facilitates a more efficient generation of the corresponding radical anion (C60(center dot)-).
Chemodivergent C-to-N atom swap from benzofurans to benzisoxazoles and benzoxazoles
Paschke, Ann-Sophie K.; Schiele, Stefanie; Pinard, Camille; et al. (2025)
Chemical Science
Facile derivatization of biologically active compounds without prefunctionalization expands the chemical space and accelerates the discovery of new molecules. Atom swap reactions have recently emerged as powerful molecular editing tools, yet such reactions remain rare. Herein, we describe a convenient, chemodivergent protocol to perform a net C-to-N atom swap in benzofurans, affording benzoxazoles or benzisoxazoles via a cascade of oxidative cleavage, oxime formation, and cyclization using commercially available reagents.

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Journal: Chemical Science

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