文献类型：期刊文献

英文题名：Well-defined N-heterocyclic carbene silver halides of 1-cyclohexyl-3-arylmethylimidazolylidenes: synthesis, structure and catalysis in A³-reaction of aldehydes, amines and alkynes

作者：Li, Yanbo[1];Chen, Xiaofeng[1];Song, Yin[1];Fang, Ling[1];Zou, Gang[1]

机构：[1]E China Univ Sci & Technol, Dept Fine Chem, Shanghai 200237, Peoples R China

年份：2011

卷号：40

期号：9

起止页码：2046

外文期刊名：DALTON TRANSACTIONS

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000287378500029)】；

基金：Financial support from the National Nature Science Foundation of China (No. 20972049) are gratefully acknowledged.

语种：英文

摘要：Structurally well-defined N-heterocyclic carbene silver chlorides and bromides supported by 1-cyclohexyl-3-benzylimidazolylidene (CyBn-NHC) or 1-cyclohexyl-3-naphthalen-2-ylmethylimidazolylidene (CyNaph-NHC) were synthesized by reaction of the corresponding imidazolium halides with silver(I) oxide while cationic bis(CyBn-NHC) silver nitrate was isolated under similar conditions using imidazolium iodide in the presence of sodium nitrate. Single-crystal X-ray diffraction revealed a dimeric structure through a nonpolar weak-hydrogen-bond supported Ag-Ag bond for 1-cyclohexyl-3-benzylimidazolylidene silver halides [(CyBn-NHC)AgX](2) (X = Cl, 1; Br, 2) but a monomeric structure for N-heterocyclic carbene silver halides with the more sterically demanding 1-cyclohexyl-3-naphthalen-2-ylmethylimidazolylidene ligand (CyNaph-NHC)AgX (X = Cl, 4; Br, 5). Cationic biscarbene silver nitrate [(CyBn-NHC)2Ag]+NO3- 3 assumed a cis orientation with respect to the two carbene ligands. The monomeric complexes (CyNaph-NHC)AgX 4 and 5 showed higher catalytic activity than the dimeric [(CyBn-NHC)AgX](2) 1 and 2 as well as the cationic biscarbene silver nitrate 3 in the model three component reaction of 3-phenylpropionaldehyde, phenylacetylene and piperidine with chloride 4 performing best and giving product in almost quantitative yield within 2 h at 100 degrees C. An explanation for the structure-activity relationship in N-heterocyclic carbene silver halide catalyzed three component reaction is given based on a slightly modified mechanism from the one in literature.