Synthesis of chiral imino- and amino-imidazolium salts and of chelating amino-N-heterocyclic carbene palladium(II) complexes

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• 作者：Alexandre Flahaut ; Jean-Pierre Baltaze ; Sylvain Roland and Pierre Mangeney
• 关键词：Chiral imino- and amino-imidazolium salts ; Chelating amino-N-heterocyclic carbenes ; Palladium(II)-metallocycles
• 刊名：Journal of Organometallic Chemistry
• 出版年：2006
• 出版时间：1 August 2006
• 年：2006
• 卷：691
• 期：16
• 页码：3498-3508
• 全文大小：272 K

文摘

A new preparation of chiral imino-imidazolium salts has been developed by condensation of chiral primary amines with 1-(2-oxo-2-phenyl-ethyl)-imidazolium salts in chloroform. This reaction gave the (E)-imino-imidazolium salts with stereoselectivities superior to 95:5. The structure of the imines were determined by NMR analyses. Reduction of the chiral (E)-imino-imidazolium salts with NaBH₄ in MeOH led to amino-imidazolium salts as a mixture of diastereomers with selectivities ranging from 84:16 to 90:10. The major diastereoisomer could be purified in some cases by crystallization and the absolute configurations were determined by X-ray diffraction. Chelating amino-N-heterocyclic carbene dichloro palladium(II) complexes were obtained in two steps via formation of the corresponding silver(I) complexes and reaction of these latters with bis(acetonitrile)dichloropalladium. Crystal structure details of a cis-dichloro amino-imidazol-2-ylidene palladium complex are presented and confirmed the formation of a six-membered Pd-metallocycle.