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1. Copper( i )-catalyzed highly enantioselective [3 + 3]-cycloaddition of γ-alkyl enoldiazoacetates with nitrones

   https://doi.org/10.1039/D0QO00539H  

   Dong, Kuiyong; Xu, Xinfang; Doyle, Michael P. (June 2020, Organic Chemistry Frontiers)

   null (Ed.)

   Chiral copper( i ) catalysts are preferred over chiral dirhodium( ii ) catalysts for [3 + 3]-cycloaddition reactions of γ-alkyl-substituted enoldiazoacetates compounds with nitrones. Using the In-SaBox ligand these reactions effectively produce cis -3,6-dihydro-1,2-oxazine derivatives under mild conditions in high yield and with exceptional stereocontrol, and enantioselectivity increases with the size of the γ-substituent. Mechanistic studies show that cycloaddition occurs solely through the formation of ( Z )-γ-substituted metallo-enolcarbene intermediates that are catalytically gennerated from both ( Z )- and ( E )-γ-substituted enoldiazoactates via donor–acceptor cyclopropene intermediates. 

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2. Atomic data calculations for Au i –Au iii and exploration in the application of collisional-radiative theory to laboratory and neutron star merger plasmas

   https://doi.org/10.1093/mnras/stab3285  

   McCann, Michael; Bromley, S; Loch, S D; Ballance, C P (December 2021, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Neutron binary star mergers have long been proposed as sufficiently neutron rich environments that could support the synthesis of rapid neutron capture elements (r-process elements) such as gold. However, the literature reveals that beyond neutral and singly ionized systems, there is an incompleteness of atomic data for the remaining ion stages of importance for mergers. In this work, we report on relativistic atomic structure calculations for Au i–Au iii using the grasp0 codes. Comparisons to calculations using the Flexible Atomic Code suggest uncertainties on average of 9.2 per cent, 5.7 per cent, and 3.8 per cent for Au i–Au iii level energies. Agreement around ∼50 per cent is achieved between our computed A-values and those in the literature, where available. Using the grasp0 structure of Au i, we calculated electron-impact excitation rate coefficients and use a collisional-radiative model to explore the excitation dynamics and line ratio diagnostics possible in neutron star merger environments. We find that proper accounting of metastable populations is critical for extracting useful information from ultraviolet–visible line ratio diagnostics of Au i. As a test of our data, we applied our electron-impact data to study a gold hollow cathode spectrum in the literature and diagnosed the plasma conditions as Te = 3.1 ± 1.2 eV and $$n_\textrm {e} = 2.7^{+1.3}_{-0.9}\times 10^{13}$$ cm−3. 

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3. HNTf ₂ -Catalyzed Formal [3 + 2] Cycloaddition of Vinyldiazoacetates to Indole-Substituted Diazo Compounds and Their Conversion to Carbazoles

   https://doi.org/10.1021/acs.orglett.4c01628  

   Bao, Ming; Carriola, Diana_Victoria Navarrete; Arman, Hadi; Doyle, Michael P (June 2024, Organic Letters)

   Triflimide catalysis of the [3 + 2]-cycloaddition of 3-indolymethanols with vinyldiazoacetates provides general access to β-tetrahydrocyclopenta[b]indol-substituted α-diazoesters. Initiated by addition of the in situ generated vinylogous iminium electrophile from 3-indolymethanol to the vinylogous position of the vinyldiazo compound and completed by intramolecular cyclization from the vinyldiazonium ion intermediate, this transformation occurs in good yields and excellent diastereoselectivity with a broad substrate scope under mild conditions. The resulting α-diazoesters undergo Rh2(OAc)4-catalyzed substrate-dependent 1,2-migration to form multisubstituted carbazoles in high yields. 

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4. Facile generation of bridged medium-sized polycyclic systems by rhodium-catalysed intramolecular (3+2) dipolar cycloadditions

   https://doi.org/10.1038/s41467-021-25513-7  

   Hou, Bao-Long; Wong, Jonathan J.; Lv, Na; Wang, Yong-Qiang; Houk, K. N.; Li, Chuang-Chuang (December 2021, Nature Communications)

   Abstract Bridged medium-sized bicyclo[m.n.2] ring systems are common in natural products and potent pharmaceuticals, and pose a great synthetic challenge. Chemistry for making bicyclo[m.n.2] ring systems remains underdeveloped. Currently, there are no general reactions available for the single-step synthesis of various bridged bicyclo[m.n.2] ring systems from acyclic precursors. Here, we report an unusual type II intramolecular (3+2) dipolar cycloaddition strategy for the syntheses of various bridged bicyclo[m.n.2] ring systems. This rhodium-catalysed cascade reaction provides a relatively general strategy for the direct and efficient regioselective and diastereoselective synthesis of highly functionalized and synthetically challenging bridged medium-sized polycyclic systems. Asymmetric total synthesis of nakafuran-8 was accomplished using this method as a key step. Quantum mechanical calculations demonstrate the mechanism of this transformation and the origins of its multiple selectivities. This reaction will inspire the design of the strategies to make complex bioactive molecules with bridged medium-sized polycyclic systems. 

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5. Unusually short Au( iii )⋯Au( iii ) aurophilic contacts between anions. Necessity of counterions

   https://doi.org/10.1039/D5DT00879D  

   Scheiner, Steve; Michalczyk, Mariusz; Zierkiewicz, Wiktor (June 2025, Dalton Transactions)

   The occurrence of these anion⋯anion dimers in the crystal structure are dependent on the presence of counterions as the attraction between two Au(iii) centers is insufficient to override the coulombic repulsion. 

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