Stereoselective pinacol coupling of planar chiral (benzaldehyde)Cr(CO)3, (benzaldimine)Cr(CO)3, ferrocenecarboxaldehyde and (dienal)Fe(CO)3 complexes with samarium diiodide
作者:Nobukazu Taniguchi、Motokazu Uemura
DOI:10.1016/s0040-4020(98)00778-9
日期:1998.10
intermolecular pinacol coupling of the planar chiral tricarbonylchromium complexes of o-substituted benzaldehydes or benzaldimines with samarium(II) diiodide in THF produces exclusively threo 1,2-diols or 1,2-diamines in an optically pure form, while the corresponding racemico-substituted benzaldehyde or benzaldimine chromium complexes give a mixture of threo and erythro pinacol coupling products in a various
C 2 symmetrical diamines are efficiently obtained by reductive coupling of imines with the couple Zn/Me3SiCl. This high yielding method is very practical and cheap for large scale preparation.
通过 Zn/Me3SiCl 与亚胺的还原偶联,可以高效地获得 C 2 对称二胺。这种高产率方法非常实用,而且成本低廉,适合大规模制备。
Synthesis of Enantiomerically Pure 1,2-Diamines by Reductive Coupling of Tricarbony(benzaldimine)chromium Complexes
作者:Nobukazu Taniguchi、Motokazu Uemura
DOI:10.1055/s-1997-721
日期:——
Enantiomerically pure 1,2-diamines are prepared by intermolecular pinacol coupling of planar chiral (benzaldimine)Cr(CO)3 complexes with samarium(II) diiodide.
radicals, enabling a series of important reactions in synthetic chemistry, such as the reductivecoupling of aldehydes, ketones, and imines, the allylation of aldehydes, the Barbier reaction, reductive arylation, and aldehyde–aniline coupling. We also present evidence to support the ketyl radicals being formed via photoinduced intermolecular electron transfer from the tertiary amine to aryl aldehydes.
A Bicyclic N-Heterocyclic Carbene as a Bulky but Accessible Ligand: Application to the Copper-Catalyzed Borylations of Aryl Halides
作者:Shin Ando、Hirofumi Matsunaga、Tadao Ishizuka
DOI:10.1021/acs.joc.5b01721
日期:2015.10.2
Imidazol-2-ylidene and imidazolin-2-ylidene are frequently employed as the core structures of N-heterocyclic carbene (NHC) ligands, because these have two nitrogen sites adjacent to carbenic carbons. The electronic and steric effects of N-substituents to a bound metal have been aptly studied, and bulky substituents have commonly been introduced on nitrogen(s). However, too much bulkiness can sometimes result in an ineffectiveness of the hindered substrates. In this study, we thoroughly compared our original bicyclic NHC, which has bulky substituents on its noncarbenic carbons, with ubiquitous NHC ligands to probe its steric properties. A well-defined bicyclic NHC CuCl complex was successfully synthesized and applied to the copper-catalyzed borylations of aryl halides at ambient temperature. A bicyclic NHC CuCl proved to be a better catalyst than commonly used NHC ligand-Cu complexes, particularly for sterically hindered substrates, which suggested that the bicyclic NHC ligand offered a bulky but accessible environment to the bound copper.