First N-Heterocyclic Carbenes Relying on the Triazolone Structural Motif: Syntheses, Modifications and Reactivity

Autor:	Janina Diekmann, Markus Jonek, Christian Ganter
Rok vydání:	2015
Předmět:	Tolman electronic parameter Chemistry Organic Chemistry Cationic polymerization General Chemistry Nuclear magnetic resonance spectroscopy Tautomer Medicinal chemistry Catalysis Carboximidate chemistry.chemical_compound Deprotonation Organic chemistry Reactivity (chemistry) Carbene
Zdroj:	Chemistry - A European Journal. 21:15759-15768
ISSN:	0947-6539
DOI:	10.1002/chem.201502685
Popis:	4-Phenylsemicarbazide and 1,5-diphenylcarbazide are suitable starting materials for the syntheses of N-heterocyclic carbene (NHC) compounds with new backbone structures. In the first case, cyclisation and subsequent methylation leads to a cationic precursor whose deprotonation affords the triazolon-ylidene 2, which was converted to the corresponding sulfur and selenium adducts and a range of metal complexes. In contrast, cyclisation of diphenylcarbazide affords a neutral betain-type NHC-precursor 7, which is not in equilibrium with its carbene tautomer 7a. Precursor 7 can either be deprotonated to give the anionic NHC 8 or methylated at the N or O atom of the backbone resulting in two isomeric cationic species 16 and 20. Deprotonation of the latter two provides neutral NHC compounds with a carboxamide or carboximidate backbone, respectively. The ligand properties of the new NHC compounds were evaluated by IR and (77) Se NMR spectroscopy. Tolman electronic parameter (TEP) values range from 2050 to 2063 cm(-1) with the anionic NHC 8 being the best overall donor.
Databáze:	OpenAIRE
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