A Change from Kinetic to Thermodynamic Control Enables trans-Selective Stereochemical Editing of Vicinal Diols

2021 ◽  
Author(s):  
Yu-An Zhang ◽  
Xin Gu ◽  
Alison E. Wendlandt
Keyword(s):  
Thermodynamic Control ◽  
Vicinal Diols

Stereodivergent Alkyne Hydrofluorination Using a Simple Practical Reagent

2020 ◽  
Author(s):  
Rui Guo ◽  
Xiaotian Qi ◽  
Hengye Xiang ◽  
Paul Geaneoates ◽  
Ruihan Wang ◽  
...  
Keyword(s):  
Bond Formation ◽  
Biologically Active ◽  
Dft Studies ◽  
Thermodynamic Control ◽  
Important Goal ◽  
Peptide Bonds ◽  
Metal Free ◽  
Vinyl Cation ◽  
E And Z Isomers ◽  
Vinyl Fluorides

Vinyl fluorides play an important role in drug development as they serve as bioisosteres for peptide bonds and are found in a range of biologically active molecules. The discovery of safe, general and practical procedures to prepare vinyl fluorides remains an important goal and challenge for synthetic chemistry. Here we introduce an inexpensive and easily-handled reagent and report simple, scalable, and metal-free protocols for the regioselective and stereodivergent hydrofluorination of alkynes to access both the E and Z isomers of vinyl fluorides. These conditions were suitable for a diverse collection of alkynes, including several highly-functionalized pharmaceutical derivatives. Mechanistic and DFT studies support C–F bond formation through a vinyl cation intermediate, with the (E)- and (Z)-hydrofluorination products forming under kinetic and thermodynamic control, respectively.<br>

Imine Based Self-Healing Hydrogel Triggered by Periodate

2020 ◽  
Author(s):  
Alexis Wolfel ◽  
Cecilia Inés Alvarez Igarzabal ◽  
Marcelo Ricardo Romero
Keyword(s):  
Functional Groups ◽  
Time Window ◽  
Crosslinking Reaction ◽  
Self Healing ◽  
Swelling Properties ◽  
Covalent Bonds ◽  
Smart Systems ◽  
Primary Amino ◽  
Vicinal Diols ◽  
Aldehyde Groups

<p>Design of materials with novel sensitivities and smart behaviour is important for the development of smart systems with automated responsiveness. We have recently reported the synthesis of hydrogels, cross-linked by <i>N,N'</i>-diallyltartardiamide (DAT). The covalent DAT-crosslinking points have vicinal diols which can be easily cleaved with periodate, generating valuable a-oxo-aldehyde functional groups, useful for further chemical modification. Based on those findings, we envisioned that a self-healable hydrogel could be obtained by incorporation of primary amino functional groups, from <a>2-aminoethyl methacrylate </a>hydrochloride (AEMA), coexisting with DAT into the same network. The a-oxo-aldehyde groups generated after the reaction with periodate would arise in the immediate environment of amine groups to form imine cross-links. For this purpose, DAT-crosslinked hydrogels were synthesized and carefully characterized. The cleavage of DAT-crosslinks with periodate promoted changes in the mechanical and swelling properties of the materials. As expected, a self-healing behavior was observed, based on the spontaneous formation of imine covalent bonds. In addition, we surprisingly found a combination of fast vicinal diols cleavage and a low speed self-crosslinking reaction by imine formation. Consequently, it was found a time-window in which a periodate-treated polymer was obtained in a transient liquid state, which can be exploited to choose the final shape of the material, before automated gelling. The singular properties attained on these hydrogels could be useful for developing sensors, actuators, among other smart systems.</p>

scholarly journals Computational exploration of heterometal substitution into the decaniobate framework, [Nb10O28]6−

2021 ◽  
Author(s):  
C. André Ohlin
Keyword(s):  
Spin State ◽  
Thermodynamic Control ◽  
Computational Exploration

The relative energetics of isomers of [MzNb9O28]11−z− is investigated computationally; new synthetic targets are identified, thermodynamic control is discussed, and prediction of spin state is investigated.

scholarly journals Mechanism of loss of thermodynamic control in mitochondria due to hyperthyroidism and temperature.

1992 ◽  
Vol 267 (22) ◽  
pp. 15348-15355
Author(s):  
S Luvisetto ◽  
I Schmehl ◽  
E Intravaia ◽  
E Conti ◽  
G.F. Azzone
Keyword(s):  
Thermodynamic Control
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