4,5‐Disubstituted N,N′‐Di‐tert‐alkyl Imidazolium Salts: New Synthesis and Structural Features

Grishina, Anastasia A.; Polyakova, Svetlana M.; Kunetskiy, Roman A.; Cı́sařová, Ivana; Lyapkalo, Ilya M.

doi:10.1002/chem.201002805

Cited by 26 publications

(27 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This resulted in the thiadiazole 16 a,i nt he elimination of the Cp* ligand and in af ormal Ti species[ Cp*Ti] with only one Cp* ligand (Scheme 12). The eliminated Cp* ligand was identified as decamethylfulvalene (Cp* 2 ), [31] tetramethylfulvene [32] and pentamethylcyclopentadiene (Cp*H), [33] by comparison of the typical NMR signals to those published in the literature (below all three species are mentioned as [Cp*] for ab etter readability). In order to complete this conversion the mixture was warmed to 60 8Cf or 38 h. Afterwards, we identified [Cp*],t he formal [Cp*Ti] species, the thiadiazole 16 a and, unfortunately,s till 15 a.T hus, Cp* 2 TiCl 2 (13)s eems to be necessary for the conversion of 15 a to 16 a.T ot est this assumption,w ed issolved pure 15 a and warmed it to 85 8C.…”

Section: Attempts To Separate [Cp* 2 M] From the Coupled Nitrilesmentioning

confidence: 99%

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

Becker

Reiß

Altenburger

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

In this work the reactivity of 1-metalla-2,5-diaza-cyclopenta-2,4-dienes of group 4 metallocenes, especially of the pyridyl-substituted examples, towards small molecules is investigated. The addition of H2 , CO2 , Ph-C≡N, 2-py-C≡N, 1,3-dicyanobenzene or 2,6-dicyanopyridine results in exchange reactions, which are accompanied by the elimination of a nitrile. For CO2 , a coordination to the five-membered cycle occurs in case of Cp*2 Zr(N=C(2-py)-C(2-py)=N). A 1,4-diaza-buta-1,3-diene complex is formed by H-transfer in the conversion of the analogous titanocene compound with CH3 -C≡N, PhCH2 -C≡N or acetone. For CH3 -C≡N a coupling product of three acetonitrile molecules is established additionally. In order to split off the metallocene from the coupled nitriles, we examined reactions with HCl, PhPCl2 , PhPSCl2 and SOCl2 . In the last case, the respective thiadiazole oxides and the metallocene dichlorides were obtained. A subsequent reaction produced thiadiazoles.

show abstract

Section: Attempts To Separate [Cp* 2 M] From the Coupled Nitrilesmentioning

confidence: 99%

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

Becker

Reiß

Altenburger

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Hier möchten wir über die Herstellung von Borylradikalen wie 11 c berichten, die das sterisch anspruchsvolle und stark nukleophile Carben 1,3‐Di‐ tert ‐butyl‐4,5‐dimethylimidazolin‐2‐yliden ( 8 ) enthalten, was ebenfalls zu senkrecht zueinander orientierten, aber invers polarisierten NHC‐ und Boryl‐Fragmente führen sollte; diese Situation kann durch die kanonische Formel B beschrieben werden (Abbildung ). Es ist selbstredend, dass ähnliche mesomere Grenzstrukturen in unterschiedlichem Maße für die Radikale 1 – 7 in Betracht gezogen werden müssen (siehe unten).…”

Section: Figureunclassified

Durch N‐heterocyclische Carbene stabilisierte Borylradikale

et al. 2016

View full text Add to dashboard Cite

Die Reaktion von 2-(Trimethylsilyl)imidazoliumtriflat 9 mit Diarylborhalogeniden (4-R-C 6 H 4 ) 2 BX (R = H, X = Br;R = CH 3 ,X = Cl;R = CF 3 ,X = Cl) führte zu den NHC-stabilisierten Boreniumkationen 10 a-c.C yclovoltammetrische Untersuchungen offenbarten eine lineare Korrelation zwischen den Hammett-Parametern s p der para-Substituenten und den Halbstufenpotentialen. Die chemische Reduktion mittels Decamethylcobaltocen, [(C 5 Me 5 ) 2 Co],l ieferte die entsprechenden Radikale 11 a-c;ihre Charakterisierung durch EPR-Spektroskopie bestätigte den paramagnetischen Charakter von 11 a-c und ergab große Hyperfeinkopplungskonstanten zu den Bor-Isotopen 11 Bu nd 10 B, während die Delokalisierung des ungepaarten Elektrons in das NHC vernachlässigbar ist. DFT-Berechnungen der Anteile der Spindichteverteilung zwischen dem Carben (NHC) und dem Borylfragment (BR 2 )o ffenbarte für 11 a-c ein Spindichteverhältnis (BR 2 /NHC) von ca. 9:1, wodurch ihr eindeutiger Borylcharakter unterstrichen wird. Die Molekülstruktur der stabilsten Spezies 11 c wurded urchR çntgenstrukturanalyse bestimmt.

show abstract

“…Further loss of molecular nitrogen from the triazene intermediate generally occurs under heating or acidic conditions to afford cyclic guanidines or guanidinium salts. [40,41] This reaction thus appears as a valuable strategy for the introduction of a nitrogen atom onto a carbenic center (formally as a nitrene moiety), but, to the best of our knowledge, it has been applied mainly to 5-membered (benz)imidazol(in)-2ylidenes, and to the notable case of the diamidocarbene A. [42] In our experiment, the reaction of [1]·Li with benzyl azide was found to be complete within less than one hour, giving an anionic triazene intermediate that was decomposed in situ by the addition of a small excess of hydrogen chloride, to give compound 11, which is globally neutral and was easily isolated in 78 % yield after purification by flash chromatography.…”

Section: Nhcmentioning

confidence: 99%

The Ambivalent Chemistry of a Free Anionic N‐Heterocyclic Carbene Decorated with a Malonate Backbone: The Plus of a Negative Charge

César

Labat

Miqueu

et al. 2013

Chemistry A European J

View full text Add to dashboard Cite

The anionic heterocycle "[maloNHC](-)", ([1](-)), is the archetype of a growing family of N-heterocyclic carbenes incorporating an anionic backbone; here, a malonate group. A comprehensive experimental exploration of its chemistry as a free entity (in the form of its lithium salt [1]·Li) is presented, and rationalized using DFT calculations at the B3LYP/6-31+G** level of theory. For the sake of comparison, similar computations were performed on other representative carbene types. Reactions of [1]·Li with a broad series of electrophilic reagents were used to ascertain its intrinsic nature as a nucleophilic carbene. Unexpectedly, [1]·Li was also seen to react with the nucleophilic tert-butylisocyanide, to give an anionic ketenimine, which could be subsequently derivatized, either into an imine by protonation of the ketenimine moiety, or into a neutral ketenimine by alkylation of the intracyclic malonate moiety. Further experiments on the electrophilic behavior of [1]·Li revealed its unexpected reactivity toward p-chlorobenzaldehyde, resulting in a formal C-H activation and the first structurally characterized keto-tautomer of the Breslow intermediate. Finally, [1]·Li remarkably activates polar E-H bonds, including N-H bonds from ammonia and amines, Si-H bonds, and B-H bonds. Importantly, DFT calculations indicate the importance of counterion effects. In particular, the key to the observed reactivity appears to be a modulation of energy levels associated with a dynamic variability of the Li-O distance between the remote malonate group and the counterion.

show abstract

4,5‐Disubstituted N,N′‐Di‐tert‐alkyl Imidazolium Salts: New Synthesis and Structural Features

Cited by 26 publications

References 71 publications

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

Durch N‐heterocyclische Carbene stabilisierte Borylradikale

The Ambivalent Chemistry of a Free Anionic N‐Heterocyclic Carbene Decorated with a Malonate Backbone: The Plus of a Negative Charge

Contact Info

Product

Resources

About