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Synthesis of 4- and 4,5-functionalized imidazol-2-ylidenes from a single 4,5-unsubstituted imidazol-2-ylidene.

ABSTRACT: Using the nucleophilicity of NHCs and aNHCs, as well as the leaving group ability of the former, the carbon-carbon double bond of imidazol-2-ylidenes can be readily mono- and difunctionalized. These results provide also a new light on the formation of abnormal carbene adducts from classical unsaturated NHCs.

SUBMITTER: Mendoza-Espinosa D

PROVIDER: S-EPMC3134311 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Synthesis of 4- and 4,5-functionalized imidazol-2-ylidenes from a single 4,5-unsubstituted imidazol-2-ylidene.

Mendoza-Espinosa Daniel D Donnadieu Bruno B Bertrand Guy G

Journal of the American Chemical Society 20100601 21

Using the nucleophilicity of NHCs and aNHCs, as well as the leaving group ability of the former, the carbon-carbon double bond of imidazol-2-ylidenes can be readily mono- and difunctionalized. These results provide also a new light on the formation of abnormal carbene adducts from classical unsaturated NHCs. ...[more]

PMID: 20443633

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Cobalt 1,3-Diisopropyl-1H-imidazol-2-ylidene Complexes: Synthesis, Solid-State Structures, and Quantum Chemistry Calculations.

Project description:The reaction of (?(5)-C(5)H(5))Co(PPh(3))(2) with 1,3-bis(isopropyl)imidazol-2-ylidene (Im(i)Pr(2)) leads to the formation of (?(5)-C(5)H(5))Co(PPh(3))(Im(i)Pr(2)). In a similar fashion (?(5)-C(5)H(5))Co(Im(i)Pr(2))(CO) is formed from (?(5)-C(5)H(5))Co(CO)(2). The barrier to rotation about the Co-C(carbene) bond in the latter complex has been determined by variable-temperature (1)H NMR spectroscopy (13.6 kcal/mol) and by computation (13.3 kcal/mol). The structural and dynamic properties of (?(5)-C(5)H(5))Co(ImMe(2))(CO) (ImMe(2) = 1,3-dimethylimidazol-2-ylidene) and (?(5)-C(5)H(5))Co(ImAr(2))(CO) (ImAr(2) = 1,3-dimesityl-2-ylidene) were examined by quantum chemistry calculations.

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Synthesis of 3-substituted isoxazolidin-4-ols using hydroboration-oxidation reactions of 4,5-unsubstituted 2,3-dihydroisoxazoles.

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Project description:A combined crystallographic database and computational chemistry analyses of tetrahedral cobalt (Co) carbonyl (CO) complexes bearing substituted imidazol-2-ylidene (Im) ligands were studied. These group of compounds are potential catalysts in the hydroformylation of alkenes as well as effective precursors for both chemical vapour deposition and atomic layer deposition in integrated circuit manufacture. A substructure search revealed seventeen (17) crystal structures in the Cambridge Structural Database (CSD). Generally, there was a positive correlation between the Im-Co bond length and the Co-CO bond length implying that a strong Im-CO bonding interaction could give rise to a more stable carbonyl complex. The gas phase structures of these complexes were further studied computationally at the BP86 level of the density functional theory. The def2-TZVPP basis set was used for cobalt with 6-31G (d,p) for all other atoms. It was observed that the Co-CO bond length increased with increase in bulkiness of alkyl substituents at the ortho positions of the Im ligands. Subsequent natural bond orbital (NBO) and chemical reactivity parameter analyses revealed that the chemical softness, electronic chemical potential and the ease of ionization also increased with increase in bulkiness of the alkyl substituents. This property has useful applications in catalytic systems and for the design of precursors in integrated circuit manufacture.

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4,5-Bis(1H-imidazol-1-ylmeth-yl)acridine monohydrate.

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4,5-Diphenyl-2-p-tolyl-1H-imidazol-3-ium nitrate.

Project description:In the cation of the title compound, C(22)H(19)N(2) (+)·NO(3) (-), the N atom in the 3-position of the imidazole is protonated. The three pendant aromatic rings are twisted from the plane of the imadazolium ring by dihedral angles of 38.1 (1), 43.74 (9) and 20.4 (1)°. In the crystal structure, N-H⋯O and N-H⋯(O,O) hydrogen bonds link the mol-ecules to form an infinite one-dimensional chain parallel to the c axis.

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