We report a highly
selective substitution of silicon-bound methoxy
groups by primary lithium amides. This unusual reactivity is possible
because of the formation of particularly stable lithium methoxide,
which compensates for the decreased Si–N bond enthalpy compared
to Si–O bonds. In contrast to substitution reactions on halosilanes,
highly selective monosubstitutions under mild conditions are possible,
even in the presence of further reactive methoxy groups. A combination
of experiments and density functional theory calculations was carried
out in order to get an extensive understanding of the reaction. The
calculations reveal a possible reaction mechanism with considerably
low activation barriers and the entry of the nucleophile to be the
rate-determining step. The low activation energies allow for the substitutions
to be carried out at low temperatures, therefore preventing side reactions
from occurring. The presented investigations expand the view of fundamental
transformation processes on silicon and give access to a wide variety
of functionalized silicon-based building blocks for various fields
of chemistry.
Despite the effectiveness of COVID-19 vaccines, there is still an urgent need for discovering new anti-viral drugs to address the awful spread and transmission of the rapidly modifiable virus. In this study, the ability of a small library of enantiomerically pure spirooxindolopyrrolidine-grafted piperidones to inhibit the main protease of SARS-CoV-2 (Mpro) is evaluated. These spiroheterocycles were synthesized by 1,3-dipolar cycloaddition of various stabilized azomethine ylides with chiral dipolarophiles derived from N-[(S)-(-)-methylbenzyl]-4-piperidone. The absolute configuration of contiguous carbons was confirmed by a single crystal X-ray diffraction analysis. The binding of these compounds to SARS-CoV-2 Mpro was investigated using molecular docking and molecular dynamics simulation. Three compounds 4a, 4b and 4e exhibited stable binding modes interacting with the key subsites of the substrate-binding pocket of SARS-CoV-2 Mpro. The synthesized compounds represent potential leads for the development of novel inhibitors of SARS-CoV-2 main protease protein for COVID-19 treatment.
The reaction of [Co2(CO)8] with an equimolar amount of the internal alkyne N-(2-butynyl)phthalimide (1-Phthalimido-2-butyne) 1 in heptane solution yields the title compound [Co2(CO)6(µ-phthalimidoCH2C≡CMe)] 2. Compound 2 has been characterized using IR, 1H and 13C NMR spectroscopy; the tetrahedrane-type cluster framework has been ascertained using a single-crystal X-ray diffraction study performed at 100 K.
The title molecular salt, C17H30NSi+·C2H5O4S−, belongs to the class of a-aminosilanes and was synthesized by the alkylation of 1-[(benzyldimethylsilyl)methyl]piperidine using diethyl sulfate. This achiral salt crystallizes in the chiral space group P21. One of the Si—C bonds in the cation is unusually long [1.9075 (12) Å], which correlates with the adjacent quaternary N+ atom and was verified by quantum chemical calculations. In the crystal, the components are linked by weak C—H...O hydrogen bonds: a Hirshfeld surface analysis was performed to further investigate these intermolecular interactions and their effects on the crystal packing.
The title compound C9H14N+·Cl−, (1), can be synthesized starting from (S)-N-methyl-1-phenylethan-1-amine (2). Compound 2 upon addition of HCl·Et2O leads to crystallization of compound 1 as colorless blocks. The configuration of compound 1 is stable as well as preserved in space group P212121. Ammonium chlorides, like the title compound, are often observed as undesirable by-products in aminosilylation of chlorosilanes. Additionally, these by-products are usually soluble in selected organic solvents, which require difficult separation steps. Therefore, detailed studies on structural features and intermolecular interactions performed by Hirshfeld atom refinement (HAR) using NoSpherA2 [Kleemiss et al. (2021). Chem. Sci.
12, 1675–1692] and Hirshfeld surface analysis were used to address structural issues on that separation problem.
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