Polarographische Untersuchungen zur Polymerisation konjugiert unges�ttigter Ketone, 1. Mitt.: Die s�urekatalysierte Polymerisation von Methylvinylketon in Methanol

Holleck, L.; Mahapatra, S.

doi:10.1007/bf01151743

Cited by 6 publications

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“…However, in the presence of 1.0 equiv of NaOH, the reproducibility of the assays is better (Figure b). This appears to be related to the neutralization of the generated HCl during the activation of the catalytic precursor, which could degrade the catalyst and/or the substrate …”

Section: Resultsmentioning

confidence: 99%

“…This appears to be related to the neutralization of the generated HCl during the activation of the catalytic precursor, which could degrade the catalyst and/or the substrate. 30 The versatility of the catalyst has been corroborated by using a variety of arylboronic acids (3a−g) bearing electron-donating and electron-withdrawing groups (Table 2). The addition of 1naphthylboronic acid to cyclohexen-2-one gives the expected product 5b in good yield, both in the presence and in the absence of NaOH.…”

Section: ■ Introductionmentioning

confidence: 99%

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Preparation, Hydrogen Bonds, and Catalytic Activity in Metal-Promoted Addition of Arylboronic Acids to Enones of a Rhodium Complex Containing an NHC Ligand with an Alcohol Function

et al. 2012

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The complex RhCl(COD){3-benzyl-1-(2-hydroxy-2-phenylethyl)imidazol-2-ylidene} has been prepared by reaction of the dimer [Rh(μ-OMe)(COD)] 2 with 3-benzyl-1-(2-hydroxy-2-phenylethyl)-imidazolium chloride and characterized by X-ray diffraction analysis. The structure reveals that 75% of the molecules are associated through intermolecular O−H···Cl hydrogen bonds between the OH group of the NHC substituent of one molecule and the chloride ligand of the adjacent molecule. This complex catalyzes the addition of arylboronic acids to cyclic and acyclic enones in anhydrous toluene. The alcohol function of the substituent of the NHC ligand plays the role assigned to water in previous cases. ■ INTRODUCTIONThe chemistry of N-heterocyclic carbenes (NHCs) is a field of great current interest due to the transversal applications of the NHC complexes, including homogeneous catalysis, 1 antimicrobial and cytotoxic agents, 2 photoactive sites in luminescent materials for self-assembly into liquid crystalline materials and metallosupramolecular structures, and synthons for molecular switches and conducting polymeric materials. 3 Although several methods have been developed for the preparation of complexes containing these ligands, deprotonation of imidazolium salts is the most used synthetic pathway. 4 The vast majority of reported NHC ligands are substituted at nitrogens by alkyl or aryl groups. Imidazolium salts with carbonyl, 5 pyridyl, 6 pyrazolyl, 7 amine, 8 and phosphine 9 substituents are also known. They can be deprotonated and are thus suitable for the preparation of metal complexes.The catalytic transformations usually take place at the metal center. However, there is an increasing number of reactions involving both the metal center and an acidic hydrogen atom of the ligands, 10 which can further form hydrogen bonds. It has been found that processes involving passive diffusion depend primarily on the hydrogen-bonding capacity or polar surface area of a drug solute. 11 Intermolecular hydrogen bonds also play an important role in the design and engineering of architectures of many polymeric materials. Hydrogen bonding can affect the chain length, chain packing, rigidity, and molecular order. 12 In addition, the induction and stabilization of liquid crystallinity by hydrogen bonding has been shown. 13 As a consequence of these observations, the preparation of transition-metal complexes with N-heterocyclic carbenes bearing acidic substituents, such as alcohols, at the N center constitutes a special challenge.Alcohol-functionalized imidazolium salts are readily accessible by the nucleophilic opening of epoxides. 14 However, alcohol-functionalized imidazolylidene transition-metal complexes are scarce. 15 In order to justify this, it has been argued that the alcohol function is more acidic than the heterocycle. Thus, the single deprotonation leads to zwitterionic alcoholate imidazolium derivatives. 16 The hexahydride complex OsH 6 (P i Pr 3 ) 2 is basic enough to produce the deprotonation of imidazolium salts, generating famil...

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Preparation, Hydrogen Bonds, and Catalytic Activity in Metal-Promoted Addition of Arylboronic Acids to Enones of a Rhodium Complex Containing an NHC Ligand with an Alcohol Function

et al. 2012

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“…Aus dem aufgezeigten polarographischen Verhalten, wie der pH-Abhangigkeit des Halbstufenpotentials, der Beeinfluobarkeit der Kurven durch grenzflachenaktive Zusatze mit den dabei auftretenden Katalyse-und Inhibitionseffekten sowie aus den Effekten bei Variation von Leitsalzen [S] und Losungsmitteln [7] (protische und aprotische), ergeben sich Einblicke in den Reduktions-Chemismus, der in Abb. 8…”

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Zur Protonierungsproblematik bei Elektrodenprozessen—Untersuchungen mit Diazoaminobenzolen und ungesättigten Ketonen

Holleck

Kazemifard

Mahapatra

1972

Chemie Ingenieur Technik

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Polymerization of vinyl ketones

Lyons

1972

J. Polym. Sci. Macromol. Rev.

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Polarographische Untersuchungen zur Polymerisation konjugiert unges�ttigter Ketone, 1. Mitt.: Die s�urekatalysierte Polymerisation von Methylvinylketon in Methanol

Cited by 6 publications

References 0 publications

Preparation, Hydrogen Bonds, and Catalytic Activity in Metal-Promoted Addition of Arylboronic Acids to Enones of a Rhodium Complex Containing an NHC Ligand with an Alcohol Function

Preparation, Hydrogen Bonds, and Catalytic Activity in Metal-Promoted Addition of Arylboronic Acids to Enones of a Rhodium Complex Containing an NHC Ligand with an Alcohol Function

Zur Protonierungsproblematik bei Elektrodenprozessen—Untersuchungen mit Diazoaminobenzolen und ungesättigten Ketonen

Polymerization of vinyl ketones

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