A General Decomposition Pathway for Phosphine-Stabilized Metathesis Catalysts: Lewis Donors Accelerate Methylidene Abstraction

A study was carried out on the solvolysis of 1-adamantyl chlorothioformate (1-AdSCOCl, 1) in hydroxylic solvents. The rate constants of the solvolysis of 1 were well correlated using the Grunwald–Winstein equation in all of the 20 solvents (R = 0.985). The solvolyses of 1 were analyzed as the following two competing reactions: the solvolysis ionization pathway through the intermediate (1-AdSCO)+ (carboxylium ion) stabilized by the loss of chloride ions due to nucleophilic solvation and the solvolysis–decomposition pathway through the intermediate 1-Ad+Cl− ion pairs (carbocation) with the loss of carbonyl sulfide. In addition, the rate constants (kexp) for the solvolysis of 1 were separated into k1-Ad+Cl− and k1-AdSCO+Cl− through a product study and applied to the Grunwald–Winstein equation to obtain the sensitivity (m-value) to change in solvent ionizing power. For binary hydroxylic solvents, the selectivities (S) for the formation of solvolysis products were very similar to those of the 1-adamantyl derivatives discussed previously. The kinetic solvent isotope effects (KSIEs), salt effects and activation parameters for the solvolyses of 1 were also determined. These observations are compared with those previously reported for the solvolyses of 1-adamantyl chloroformate (1-AdOCOCl, 2). The reasons for change in reaction channels are discussed in terms of the gas-phase stabilities of acylium ions calculated using Gaussian 03.

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Effect of dithiocyano-methane on hexose monophosphate pathway in the respiratory metabolism of Escherichia coli

AMB Express ◽

10.1186/s13568-020-01142-z ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Yanfeng Chen ◽

Wenjie Ke ◽

Huabin Qin ◽

Siwei Chen ◽

Limei Qin ◽

...

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Control Group ◽

Respiratory Metabolism ◽

Hexose Monophosphate ◽

Hexose Monophosphate Pathway ◽

Response To Stress ◽

Glucose Decomposition ◽

Decomposition Pathway ◽

Glucose 6 Phosphate Dehydrogenase

Abstract This paper studied the inhibitory effects of dithiocyano-methane (DM) on the glucose decomposition pathway in the respiratory metabolism of Escherichia coli. We investigated the effects of DM on the activities of key enzymes (ATPase and glucose-6-phosphate dehydrogenase, G6PDH), the levels of key product (nicotinamide adenosine denucleotide hydro-phosphoric acid, NADPH), and gene expression in the hexose monophosphate pathway (HMP). The results showed that the minimum inhibitory concentration (MIC) and the minimum bactericide concentration (MBC) of DM against the tested strains were 5.86 mg/L and 11.72 mg/L, respectively. Bacteria exposed to DM at MIC demonstrated an increase in bacterial ATPase and G6PDH activities, NADPH levels, and gene expression in the HMP pathway compared to bacteria in the control group, which could be interpreted as a behavioral response to stress introduced by DM. However, DM at a lethal concentration of 10 × MIC affected glucose decomposition by inhibiting mainly the HMP pathway in E. coli.

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Nitrenium ions and trivalent boron ligands as analogues of N-heterocyclic carbenes in olefin metathesis: a computational study

Dalton Transactions ◽

10.1039/c5dt03446a ◽

2015 ◽

Vol 44 (46) ◽

pp. 20021-20026 ◽

Cited By ~ 10

Author(s):

A. Pazio ◽

K. Woźniak ◽

K. Grela ◽

B. Trzaskowski

Keyword(s):

Olefin Metathesis ◽

Computational Study ◽

Heterocyclic Carbenes ◽

Mechanistic Study ◽

Nitrenium Ions ◽

Nitrenium Ion ◽

Metathesis Catalysts

A DFT mechanistic study reveals that nitrenium ion-modified Hoveyda-like complexes are good candidates for latent metathesis catalysts, while boron-modified systems are candidates for very fast metathesis catalysts.

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