Lipase-Catalyzed Epoxy–Acid Addition and Transesterification: from Model Molecule Studies to Network Build-Up

Reactions of 19-hydroxy-, methoxy- and acetoxy-5-cholestenes Ia, IIa, IIIa were studied and compared with those previously obtained with analogous 3β-acetoxy-19-substituted 5-cholestenes Ib, IIb, IIIc. A marked difference was found in 19-acetoxy derivatives where the 3-unsubstituted compound IIIa yields exclusively the bromohydrin XVIa as a product of 6(O)π,n participation while the 3β-acetoxy derivative IIIb gives, apart from the analogous bromohydrin XVIb, also products of competing reactions: The epoxide XIIb and the bromohydrin XIIIb.

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Participation by some oxygen containing groups in hypobromous acid addition to double bond

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19833660 ◽

1983 ◽

Vol 48 (12) ◽

pp. 3660-3673 ◽

Cited By ~ 3

Author(s):

Pavel Kočovský

Keyword(s):

Double Bond ◽

Functional Groups ◽

Relative Reactivity ◽

Product Analysis ◽

Acid Addition ◽

Hypobromous Acid ◽

Electron Withdrawing Substituents

5(O)n and 6(O)π,n participations by some oxygen containing functional groups in the course of reaction with hypobromous acid have been studied on olefinic models of steroid type (I and II). The ability of these groups to participate has been compared on the basis of their relative reactivity with water (as externally attacking nucleophile) competing with participation. The results of the product analysis show that the ability to react with 5(O)n participation decreases in the order HO > CH3O ≃ CH3OCH2O > CH3CO2 > HCO2 > CH3SO3 ≥ (C2H5O)2PO2 > C6H5CO2 > O2NO ≫ CF3CO2, C2H5OCO2; in the last two functional groups is this ability completely suppressed. The 6(O)π,n participation comes in consideration only for compounds of the type II bearing the groups with the -X=O moiety which are ordered in the following sequence: C2H5OCO2 ≃ CH3CO2 ≥ (C2H5O)2PO2 > HCO2 > C6H5CO2. The remaining functional groups (CF3CO2, O2NO and CH3SO3do not undergo this process. Generally, it is valid that introduction of electron-withdrawing substituents into a participating group impedes or completely suppresses its ability to participate.

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Neighboring group participation in hypobromous acid addition to 19-substituted 5α-cholest-1-enes and in acid cleavage of their epoxy analogs

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19823062 ◽

1982 ◽

Vol 47 (11) ◽

pp. 3062-3076 ◽

Cited By ~ 3

Author(s):

Václav Černý ◽

Pavel Kočovský

Keyword(s):

Neighboring Group ◽

Group Participation ◽

Acid Addition ◽

Acid Cleavage ◽

Hypobromous Acid ◽

Neighboring Group Participation

Reactions of the title compounds (bearing an OH, OCH3 or OCOCH3 group at C(19)) involve 5(O)n, 7(O)π,n-participation by the 19-substituent or attack by an external nucleophile. The 6(O)π,n-participation does not occur. The behavior of 1,2-unsaturated (or epoxidated) compounds has been compared with the earlier described 2,3-unsaturated or epoxidated analogs. The 1,2-type is genarally less prone to participation. The reasons for this behavior are discussed.

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Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect citric acid addition

Applied Catalysis B Environmental ◽

10.1016/j.apcatb.2021.120206 ◽

2021 ◽

pp. 120206

Author(s):

Yingying Li ◽

Yong Men ◽

Shuang Liu ◽

Jinguo Wang ◽

Kang Wang ◽

...

Keyword(s):

Citric Acid ◽

Co2 Methanation ◽

Acid Addition

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High-level exogenous glutamic acid-independent production of poly-(γ-glutamic acid) with organic acid addition in a new isolated Bacillus subtilis C10

Bioresource Technology ◽

10.1016/j.biortech.2011.11.085 ◽

2012 ◽

Vol 116 ◽

pp. 241-246 ◽

Cited By ~ 40

Author(s):

Huili Zhang ◽

Jianzhong Zhu ◽

Xiangcheng Zhu ◽

Jin Cai ◽

Anyi Zhang ◽

...

Keyword(s):

Bacillus Subtilis ◽

Glutamic Acid ◽

Organic Acid ◽

Acid Addition ◽

High Level

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Modified-TiO2 Photocatalyst Supported on β-SiC Foams for the Elimination of Gaseous Diethyl Sulfide as an Analog for Chemical Warfare Agent: Towards the Development of a Photoreactor Prototype

Catalysts ◽

10.3390/catal11030403 ◽

2021 ◽

Vol 11 (3) ◽

pp. 403

Author(s):

Armelle Sengele ◽

Didier Robert ◽

Nicolas Keller ◽

Valérie Keller

Keyword(s):

Photocatalytic Oxidation ◽

Chemical Warfare Agents ◽

Chemical Warfare Agent ◽

Chemical Warfare ◽

Diethyl Sulfide ◽

Tio2 Photocatalysts ◽

Doped Tio2 ◽

Model Molecule ◽

Warfare Agents ◽

Oxidation Efficiency

In the context of the increase in chemical threat due to warfare agents, the development of efficient methods for destruction of Chemical Warfare Agents (CWAs) are of first importance both for civilian and military purposes. Amongst possible methods for destruction of CWAs, photocatalytic oxidation is an alternative one. The present paper reports on the preparation of Ta and Sn doped TiO2 photocatalysts immobilized on β-SiC foams for the elimination of diethyl sulfide (DES) used as a model molecule mimicking Yperite (Mustard Gas) in gaseous phase. Photo-oxidation efficiency of doped TiO2 catalyst has been compared with TiO2-P25. Here, we demonstrate that the Sn doped-TiO2 with a Polyethylene glycol (PEG)/TiO2 ratio of 7 exhibits the best initial activity (up to 90%) but is deactivates more quickly than Ta doped-TiO2 (40% after 800 min). The activity of the catalysts is strongly influenced by the adsorption properties of the support, as β-SiC foams adsorb DES and other sulfur compounds. This adsorption makes it possible to limit the poisoning of the catalysts and to maintain an acceptable conversion rate even after ten hours under continuous DES flow. Washing with NaOH completely regenerates the catalyst after a firs treatment and even seems to “wash” it by removing impurities initially present on the foams.

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