Photochemically Promoted Aza-Diels–Alder-Type Reaction: High Catalytic Activity of the Cr(III)/Bipyridine Complex Enhanced by Visible Light Irradiation
作者:Noriyoshi Arai、Takeshi Ohkuma
DOI:10.1021/acs.joc.7b00838
日期:2017.7.21
Aza-Diels–Alder-type cycloaddition reactions between a range of N-arylimines and functionalized alkenes were effectively catalyzed by the Cr(III)/bipyridine complex under irradiation of blue light, to give the corresponding 1,2,3,4-tetrahydroquinoline derivatives in high yields with excellent diastereoselectivity. Typically, the reaction of benzylideneaniline with 1-vinyl-2-pyrrolidinone proceeded
Under open-flask conditions in the presence of commercially available FeCl3·6H2O, N,N-disubstituted anilines can be converted into diversely functionalized benzidines with yields of up to 99%. Oxidative coupling was extended to N-monosubstituted anilines, and the method was applied to the efficient preparation of 6,6′-biquinoline. Mechanistic investigations have also been performed to explain the observed
Iron-Catalyzed Hydrogen Transfer Reduction of Nitroarenes with Alcohols: Synthesis of Imines and Aza Heterocycles
作者:Jiajun Wu、Christophe Darcel
DOI:10.1021/acs.joc.0c02505
日期:2021.1.1
A straightforward and selective reduction of nitroarenes with various alcohols was efficiently developed using an iron catalyst via a hydrogentransfer methodology. This protocol led specifically to imines in 30–91% yields, with a good functional group tolerance. Noticeably, starting from o-nitroaniline derivatives, in the presence of alcohols, benzimidazoles can be obtained in 64–72% yields when the
The various imines were prepared from alcohols and amines in moderate to good yields under an air atmosphere promoted by KOH, eliminating the need for toxic transition metal catalysts. Due to its simplicity, this protocol will have wide application in synthesis.
The catalytic dehydrogenation and tandem transformation of aromatic alcohols, including oxidative coupling of alcohols and amines, were achieved successfully using a catalytic amount of organosilicon-supported titania (TiO2@PMHSIPN), which enables the efficient synthesis of aromatic aldehydes, imines, and benzimidazoles in good to excellent yields.