Journal of the American Chemical Society
DOI: 10.1021/jacs.1c12456
Juan Rueda
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01 Apr 19:42
[ASAP] In Situ Control of Crystallinity of 3D Colloidal Crystals by Tuning the Growth Kinetics of Nanoparticle Building Blocks
by Fumiko Nakagawa, Masaki Saruyama, Ryo Takahata, Ryota Sato, Kenshi Matsumoto, and Toshiharu Teranishi
11 Feb 20:11
Reversible Uptake of CO2 by Pincer Ligand Supported Dimetallynes
by Alexa Caise,
Liam P. Griffin,
Caitilín McManus,
Andreas Heilmann,
Simon Aldridge
The reversible uptake of CO2 by dimetallynes featuring ancillary hemi-labile pincer ligands is reported. Insertion into the Ge−Ge/Sn−Sn bonds yields species containing an E(CO2)E unit, with the mode of ligation of the CO2 fragment being dependent on the Group 14 element. The thermodynamics of CO2 uptake can be established through VT NMR, and the chemical consequences of reversibility demonstrated by thermodynamically-controlled exchange reactions.
Abstract
We report on the reversible uptake of carbon dioxide by dimetallynes featuring ancillary hemi-labile pincer ligands. Insertion into the Ge−Ge/Sn−Sn bonds yields species containing an E(CO2)E unit, with the mode of ligation of the CO2 fragment determined crystallographically being found to be dependent on the identity of the Group 14 element. The thermodynamics of CO2 uptake/loss can be established through VT NMR (ΔH°=+24.6(2.3) kJ mol−1, ΔS°=+64.9(3.8) J mol−1 K−1, ΔG°298=+5.3(1.9) kJ mol−1 for the loss of CO2 in the Ge case), and the chemical consequences of reversibility demonstrated by thermodynamically-controlled exchange reactions.
10 Jan 15:48
Asymmetric Hydroaminoalkylation of Alkenylazaarenes via Cooperative Photoredox and Chiral Hydrogen‐Bonding Catalysis
by Xiangpei Chai,
Xinheng Hu,
Xiaowei Zhao,
Yanli Yin,
Shanshan Cao,
Zhiyong Jiang
A highly enantioselective hydroaminoalkylation of alkenyl azaarenes is described as the first successful catalytic asymmetric conjugate addition of radicals to activated olefins to directly forge stereocenters at their β-position. The stereoselective transformation was made possible by the introduction of cooperative nonclassical H-bonding interactions, thus enabling the chiral catalyst to provide sufficient stereocontrol.
Abstract
Chiral hydrogen-bonding (H-bonding) catalytic asymmetric conjugate addition to activated olefins has been widely used to access enantioenriched molecules containing stereocenters at the β-position of the olefin activating groups. Herein, we report the first highly enantioselective radical-based manifold. Under a dual organocatalyst system involving a chiral phosphoric acid and DPZ as the photoredox sensitizer, transformations of N-arylglycines, in which aryls with CF3 substituents are introduced, with alkenyl azaarenes afforded valuable hydroaminoalkylation adducts with satisfactory results. In addition to the diversity of azaarenes, the method can be used to construct aryl-, alkyl- and silyl-substituted stereocenter. Control experiments and density functional theory calculations were performed to elucidate a plausible reaction mechanism and the origin of stereoselectivity, wherein nonclassical H-bonding interactions were found to assist chiral catalysts in offering sufficient enantiocontrol.
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