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1. Asymmetric [3+ n ]‐Cycloaddition Reactions of Donor‐Acceptor Cyclopropanes

   https://doi.org/10.1002/cctc.202301090  

   Bao, Ming; Doyle, Michael_P (November 2023, ChemCatChem)

   Abstract [3+n]‐Cycloaddition reactions that employ donor‐acceptor cyclopropanes using either chiral catalysts and racemic cyclopropanes or achiral catalysts and chiral, non‐racemic, cyclopropanes have become useful transformations for the construction of carbocyclic and heterocyclic compounds, with both processes offering mechanistic and structural advantages in ring formation. Although the vast majority of asymmetric cycloaddition reactions of donor‐acceptor cyclopropanes have been performed with racemic cyclopropane compounds catalyzed by Lewis acids with chiral ligands, optically active cyclopropane compounds can serve the same role using Lewis acids without chiral ligands. This review covers the use of chiral catalysts with racemic donor‐acceptor cyclopropanes and the use of chiral non‐racemic donor‐acceptor cyclopropanes with achiral Lewis acid catalysts. 

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2. Intra- and intermolecular Fe-catalyzed dicarbofunctionalization of vinyl cyclopropanes

   https://doi.org/10.1039/D0SC00467G  

   Liu, Lei; Lee, Wes; Yuan, Mingbin; Acha, Chris; Geherty, Michael B.; Williams, Brandon; Gutierrez, Osvaldo (March 2020, Chemical Science)

   null (Ed.)

   Design and implementation of the first (asymmetric) Fe-catalyzed intra- and intermolecular difunctionalization of vinyl cyclopropanes (VCPs) with alkyl halides and aryl Grignard reagents has been realized via a mechanistically driven approach. Mechanistic studies support the diffusion of alkyl radical intermediates out of the solvent cage to participate in an intra- or intermolecular radical cascade with a range of VCPs followed by re-entering the Fe radical cross-coupling cycle to undergo (stereo)selective C(sp 2 )–C(sp 3 ) bond formation. This work provides a proof-of-concept of the use of vinyl cyclopropanes as synthetically useful 1,5-synthons in Fe-catalyzed conjunctive cross-couplings with alkyl halides and aryl/vinyl Grignard reagents. Overall, we provide new design principles for Fe-mediated radical processes and underscore the potential of using combined computations and experiments to accelerate the development of challenging transformations. 

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3. Converting Strain Release into Aromaticity Loss for Activation of Donor–Acceptor Cyclopropanes: Generation of Quinone Methide Traps for C-Nucleophiles

   https://doi.org/10.1021/acs.orglett.4c03106  

   Shorokhov, Vitaly V; Chabuka, Beauty K; Tikhonov, Timur P; Filippova, Anastasia V; Zhokhov, Sergey S; Tafeenko, Victor A; Andreev, Ivan A; Ratmanova, Nina K; Uchuskin, Maxim G; Trushkov, Igor V; et al (September 2024, Organic Letters)

   Here, we present a new approach for the activation of donor–acceptor cyclopropanes in ring-opening reactions, which does not require the use of a Lewis or Brønsted acid as a catalyst. Donor–acceptor cyclopropanes containing a phenolic group as the donor undergo deprotonation and isomerization to form the corresponding quinone methides. This innovative strategy was applied to achieve (4 + 1)-annulation of cyclopropanes with sulfur ylides, affording functionalized dihydrobenzofurans. Additionally, the generated ortho- and para-(aza)quinone methides can be trapped by various CH-acids. 

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4. Design and Development of Fe-Catalyzed Intra- and Intermolecular Carbofunctionalization of Vinyl Cyclopropanes

   https://doi.org/10.26434/chemrxiv.9858500.v1  

   Liu, L.; Lee, W.; Yuan, M.; Acha, C.; * Geherty, M. B.; * Williams, B. * (September 2019, Chemistry preprint archive)

   Design and implementation of the first (asymmetric) Fe-catalyzed intra- and intermolecular difunctionalization of vinyl cyclopropanes (VCPs) with alkyl halides and aryl Grignard reagents has been realized via a mechanistically driven approach. Mechanistic studies support the diffusion of the alkyl radical intermediates out of the solvent cage to participate in an intra- or -intermolecular radical cascade with the VCP followed by re-entering the Fe radical cross-coupling cycle to undergo selective C(sp2)-C(sp3) bond formation. Overall, we provide new design principles for Fe-mediated radical processes and underscore the potential of using combined computations and experiments to accelerate the development of challenging transformations. 

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5. Switching CO ₂ Electroreduction Selectivity Between C ₁ and C ₂ Hydrocarbons on Cu Gas‐Diffusion Electrodes

   https://doi.org/10.1002/eem2.12307  

   Zhang, Jianfang; Li, Zhengyuan; Cai, Rui; Zhang, Tianyu; Yang, Shize; Ma, Lu; Wang, Yan; Wu, Yucheng; Wu, Jingjie (April 2022, ENERGY & ENVIRONMENTAL MATERIALS)

   Regulating the selectivity toward a target hydrocarbon product is still the focus of CO₂electroreduction. Here, we discover that the original surface Cu species in Cu gas‐diffusion electrodes plays a more important role than the surface roughness, local pH, and facet in governing the selectivity toward C₁or C₂hydrocarbons. The selectivity toward C₂H₄progressively increases, while CH₄decreases steadily upon lowering the Cu oxidation species fraction. At a relatively low electrodeposition voltage of 1.5 V, the Cu gas‐diffusion electrode with the highest Cu^δ+/Cu⁰ratio favors the pathways of hydrogenation to form CH₄with maximum Faradaic efficiency of 65.4% and partial current density of 228 mA cm⁻²at −0.83 V vs RHE. At 2.0 V, the Cu gas‐diffusion electrode with the lowest Cu^δ+/Cu⁰ratio prefers C–C coupling to form C₂₊products with Faradaic efficiency topping 80.1% at −0.75 V vs RHE, where the Faradaic efficiency of C₂H₄accounts for 46.4% and the partial current density of C₂H₄achieves 279 mA cm⁻². This work demonstrates that the selectivity from CH₄to C₂H₄is switchable by tuning surface Cu species composition of Cu gas‐diffusion electrodes. 

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