The Mechanism of the Transition Metal-catalyzed Reaction of 1,1′-Carbonyldipyrazoles with Aldehydes and Ketones

1974 ◽  
Vol 52 (13) ◽  
pp. 2367-2374 ◽  
Author(s):  
L. K. Peterson ◽  
E. Kiehlmann ◽  
A. R. Sanger ◽  
K. I. Thé
Keyword(s):  
Carbon Dioxide ◽  
Metal Ion ◽  
Substituent Effects ◽  
Amide Bond ◽  
Reaction Conditions ◽  
Aldehydes And Ketones ◽  
Amide Carbonyl ◽  
Amide Carbonyl Group ◽  
Metal Catalyzed ◽  
Metal Ion Exchange

The metal-catalyzed reaction of 1,1′-carbonyldipyrazoles with aldehydes or ketones to give 1,1′-alkylidenedipyrazoles and carbon dioxide, the latter being derived from the amide carbonyl group as shown by labeling experiments, is sensitive to electronic and to steric substituent effects. Under comparable reaction conditions, 1,1′-carbonyldiimidazole, N-acetylpyrazole, and 1-pyrazole-N,N-diethylcarbonamide do not react with acetone while pyrazole-1-carbo(N′-phenylhydrazide) yields an anilino isocyanate dimer. These results are interpreted in terms of a mechanism that involves coordination of the metal ion at the 2,2′-nitrogen atoms of the pyrazole rings and heterolytic cleavage of an amide bond, followed by formation of a carbamate intermediate, decarboxylation, and metal ion exchange. Unsymmetrically substituted 1,1′-carbonyldipyrazoles were found to equilibrate thermally with their respective symmetrical analogs by an intermolecular exchange mechanism.

Tubular Titanates: Alkali-Metal Ion-Exchange Features and Carbon Dioxide Adsorption at Room Temperature

2019 ◽  
Vol 58 (13) ◽  
pp. 5168-5174 ◽  
Author(s):  
Eri Uematsu ◽  
Atsushi Itadani ◽  
Hideki Hashimoto ◽  
Kazuyoshi Uematsu ◽  
Kenji Toda ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ion Exchange ◽  
Alkali Metal ◽  
Metal Ion ◽  
Room Temperature ◽  
Carbon Dioxide Adsorption ◽  
Alkali Metal Ion ◽  
Metal Ion Exchange

The Preparation of 1,1′-Carbonyl- and 1,1′-Sulfinyl-dipyrazoles and their Reactions with Carbonyl Compounds

1973 ◽  
Vol 51 (15) ◽  
pp. 2448-2451 ◽  
Author(s):  
K. I. The ◽  
L. K. Peterson ◽  
E. Kiehlmann
Keyword(s):  
Carbon Dioxide ◽  
Sulfur Dioxide ◽  
Carbonyl Compounds ◽  
Metal Ion ◽  
Aldehydes And Ketones

The compounds 1,1′-carbonylbis(3-methylpyrazole) (1), 1,1′-carbonylbis(3,5-dimethylpyrazole) (2), and 1,1′-sulfinyldipyrazole (3) have been prepared. They react with aldehydes and ketones in the presence of metal ion catalysts to form 1,1′-alkylidenedipyrazoles together with carbon dioxide, from 1 and 2, or sulfur dioxide, from 3. Tetrapyrazol-1-ylmethane results from the pyrolysis at 200° of 1,1′-carbonyldipyrazole in the presence of cobalt(II) chloride.

scholarly journals Base Metal Catalysts for Deoxygenative Reduction of Amides to Amines

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 490 ◽  
Author(s):  
Andrey Khalimon ◽  
Kristina Gudun ◽  
Davit Hayrapetyan
Keyword(s):  
Base Metal ◽  
Precious Metals ◽  
Building Blocks ◽  
Metal Catalysts ◽  
Environmentally Benign ◽  
Attractive Alternative ◽  
Catalytic Systems ◽  
Amide Carbonyl ◽  
Amide Carbonyl Group ◽  
Metal Catalyzed

The development of efficient methodologies for production of amines attracts significant attention from synthetic chemists, because amines serve as essential building blocks in the synthesis of many pharmaceuticals, natural products, and agrochemicals. In this regard, deoxygenative reduction of amides to amines by means of transition-metal-catalyzed hydrogenation, hydrosilylation, and hydroboration reactions represents an attractive alternative to conventional wasteful techniques based on stoichiometric reductions of the corresponding amides and imines, and reductive amination of aldehydes with metal hydride reagents. The relatively low electrophilicity of the amide carbonyl group makes this transformation more challenging compared to reduction of other carbonyl compounds, and the majority of the reported catalytic systems employ precious metals such as platinum, rhodium, iridium, and ruthenium. Despite the application of more abundant and environmentally benign base metal (Mn, Fe, Co, and Ni) complexes for deoxygenative reduction of amides have been developed to a lesser extent, such catalytic systems are of great importance. This review is focused on the current achievements in the base-metal-catalyzed deoxygenative hydrogenation, hydrosilylation, and hydroboration of amides to amines. Special attention is paid to the design of base metal catalysts and the mechanisms of such catalytic transformations.

Carbon Dioxide-Mediated C(sp2)–H Arylation of Primary and Secondary Benzylamines

2018 ◽  
Author(s):  
Mohit Kapoor ◽  
Pratibha Chand-Thakuri ◽  
Michael Young
Keyword(s):  
Carbon Dioxide ◽  
Transition Metal ◽  
Bond Activation ◽  
Bond Formation ◽  
Carbon Bond ◽  
Chelate Effect ◽  
Free Amine ◽  
Carbon Carbon Bond ◽  
New Strategy ◽  
Metal Catalyzed

Carbon-carbon bond formation by transition metal-catalyzed C–H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of <i>ortho</i>-arylbenzylamines, however, effective <i>ortho</i>-C–C bond formation from C–H bond activation of free primary and secondary benzylamines using Pd<sup>II</sup> remains an outstanding challenge. Presented herein is a new strategy for constructing <i>ortho</i>-arylated primary and secondary benzylamines mediated by carbon dioxide (CO<sub>2</sub>). The use of CO<sub>2</sub> is critical to allowing this transformation to proceed under milder conditions than previously reported, and that are necessary to furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, a chelate effect is demonstrated to facilitate selective monoarylation.

Chemistry of Unsymmetrical C1-Substituted Oxabenzonorbornadienes

2021 ◽  
Vol 17 ◽  
Author(s):  
Austin Pounder ◽  
Angel Ho ◽  
Matthew Macleod ◽  
William Tam
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Substituent Effects ◽  
Face Selectivity ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed ◽  
Synthetic Intermediate

: Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate which can be readily activated by transition metal complexes with great face selectivity due to its dual-faced nature and intrinsic angle strain on the alkene. To date, the understanding of transition-metal catalyzed reactions of OBD itself has burgeoned; however, this has not been the case for unsymmetrical OBDs. Throughout the development of these reactions, the nature of C1-substituent has proven to have a profound effect on both the reactivity and selectivity of the outcome of the reaction. Upon substitution, different modes of reactivity arise, contributing to the possibility of multiple stereo-, regio-, and in extreme cases, constitutional isomers which can provide unique means of constructing a variety of synthetically useful cyclic frameworks. To maximize selectivity, an understanding of bridgehead substituent effects is crucial. To that end, this review outlines hitherto reported examples of bridgehead substituent effects on the chemistry of unsymmetrical C1-substituted OBDs.

Bu4N+-Controlled Addition and Olefination with Ethyl 2-(Trimethylsilyl)acetate via Silicon Activation

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2401-2406 ◽  
Author(s):  
Donal O’Shea ◽  
Manas Das ◽  
Atul Manvar ◽  
Ian Fox ◽  
Dilwyn Roberts
Keyword(s):  
Room Temperature ◽  
Product Formation ◽  
Unsaturated Ester ◽  
Reaction Conditions ◽  
Diverse Range ◽  
Inorganic Cation ◽  
Tetrabutyl Ammonium ◽  
Aldehydes And Ketones ◽  
Subsequent Elimination ◽  
Hydroxy Esters

Catalytic Bu4NOAc as silicon activator of ethyl 2-(trimethylsilyl)acetate, in THF, was utilized for the synthesis of β-hydroxy esters, whereas employing catalytic Bu4NOTMS gave α,β-unsaturated esters. The established reaction conditions were applicable to a diverse range of aromatic, heteroaromatic, aliphatic aldehydes and ketones. Reactions were achieved at room temperature without taking any of the specialized precautions that are in place for other organometallics. A stepwise olefination pathway via silylated β-hydroxy esters with subsequent elimination to form the α,β-unsaturated ester has been demonstrated. The key to selective product formation lies in use of the weaker acetate activator which suppresses subsequent elimination whereas stronger TMSO– activator (and base) facilitates both addition and elimination steps. The use of tetrabutyl ammonium salts for both acetate and trimethylsilyloxide activators provide enhanced silicon activation when compared to their inorganic cation counterparts.

scholarly journals Investigation of the active site of oligosaccharyltransferase from pig liver using synthetic tripeptides as tools

1995 ◽  
Vol 312 (3) ◽  
pp. 979-985 ◽  
Author(s):  
E Bause ◽  
W Breuer ◽  
S Peters
Keyword(s):  
Hydroxy Group ◽  
Active Site ◽  
Catalytic Mechanism ◽  
Endoplasmic Reticulum Membrane ◽  
Hydrogen Binding ◽  
Ph Optimum ◽  
Pig Liver ◽  
Acceptor Activity ◽  
Amide Carbonyl ◽  
Amide Carbonyl Group

Oligosaccharyltransferase (OST), an integral component of the endoplasmic-reticulum membrane, catalyses the transfer of dolichyl diphosphate-linked oligosaccharides to specific asparagine residues forming part of the Asn-Xaa-Thr/Ser sequence. We have studied the binding and catalytic properties of the enzyme from pig liver using peptide analogues derived from the acceptor peptide N-benzoyl-Asn-Gly-Thr-NHCH3 by replacing either asparagine or threonine with amino acids differing in size, stereochemistry, polarity and ionic properties. Acceptor studies showed that analogues of asparagine and threonine with bulkier side chains impaired recognition by OST. Reduction of the beta-amide carbonyl group of asparagine yielded a derivative that, although not glycosylated, was strongly inhibitory (50% inhibition at approximately 140 microM). This inhibition may be due to ion-pair formation involving the NH3+ group and a negatively charged base at the active site. Hydroxylation of asparagine at the beta-C position increased Km and decreased Vmax, indicating an effect on both binding and catalysis. The threo configuration at the beta-C atom of the hydroxyamino acid was essential for substrate binding. A peptide derivative obtained by replacement of the threonine beta-hydroxy group with an NH2 group was found to display acceptor activity. This shows that the primary amine is able to mimic the hydroxy group during transglycosylation. The pH optimum with this derivative is shifted by approximately 1 pH unit towards the basic region, indicating that the neutral NH2 group is the reactive species. The various data are discussed in terms of the catalytic mechanism of OST, particular emphasis being placed on the role of threonine/serine in increasing the nucleophilicity of the beta-amide of asparagine through hydrogen-binding.

Alkali metal catalyzed carbon dioxide gasification of carbon

1992 ◽  
Vol 6 (4) ◽  
pp. 343-351 ◽  
Author(s):  
Toshimitsu Suzuki ◽  
Hiroyuki Ohme ◽  
Yoshihisa Watanabe
Keyword(s):  
Carbon Dioxide ◽  
Alkali Metal ◽  
Gasification Of Carbon ◽  
Metal Catalyzed ◽  
Carbon Dioxide Gasification
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