Transition-Metal-Free N–O Reduction of Oximes: A Modular Synthesis of Fluorinated Pyridines
作者:Huawen Huang、Jinhui Cai、Hao Xie、Jing Tan、Feifei Li、Guo-Jun Deng
DOI:10.1021/acs.orglett.7b01564
日期:2017.7.21
An NH4I-based reductive system has been explored to promote the oxime N–O bond cleavage and thereby enable a modular synthesis of a broad range of pharmacologically significant fluorinated pyridines. Compared with traditional condensation methods for pyridine assembly, this protocol was found to be highly regio- and chemoselective and presented broad functional group tolerance.
Efficient and convenient entry to β-hydroxy-β-trifluoromethyl-β-substituted ketones and 2,6-disubstituted 4-trifluoromethylpyridines based on the reaction of trifluoromethyl ketones with enamines or imines
The reactions of trifluoromethyl ketones with enamines or imines are described. The reaction of trifluoroacetone with enamines or imines followed by hydrolysis gave the corresponding β-hydroxy-β-trifluoromethyl-β-methyl ketones in good yields. The reaction of trifluoromethylated β-diketones with enamines in the presence of ammonium acetate gave 4-trifluoromethylated pyridines exclusively in good yields, without any detectable amount of regioisomers.
Redox‐Divergent Synthesis of Fluoroalkylated Pyridines and 2‐Pyridones through Cu‐Catalyzed N−O Cleavage of Oxime Acetates
作者:Dachang Bai、Xueli Wang、Guangfan Zheng、Xingwei Li
DOI:10.1002/anie.201802311
日期:2018.5.28
Cu‐catalyzed redox‐divergent [3+3] coupling of oxime esters with β‐CF3 enones and acrylates is described. This redox‐neutral coupling with enones and acrylates affords trifluoromethylated pyridines and pyridones, respectively. Under reductive conditions, difluoromethylated pyridines, difluoromethlated pyridones, and trifluoromethylated dihydropyridones are obtained. The reactions occur under mild conditions
4-HO-TEMPO-Catalyzed Redox Annulation of Cyclopropanols with Oxime Acetates toward Pyridine Derivatives
作者:Jun-Long Zhan、Meng-Wei Wu、Dian Wei、Bang-Yi Wei、Yu Jiang、Wei Yu、Bing Han
DOI:10.1021/acscatal.9b00832
日期:2019.5.3
for the synthesis of pyridines through the annulation of cyclopropanols and oxime acetates has been developed. This protocol features good functional group tolerance and high chemoselectivity and also promises to be efficient for the late-stage functionalization of skeletons of drugs and natural products. Mechanism studies indicate that the reaction involves the in situ generated α,β-unsaturated ketones