A palladium-catalyzed process to construct oxazoles and oxazolines with broad functional-group tolerance has been developed, and the method introduces difluoromethyl groups into heterocycles in a one-pot fashion. This system uses a carbonyl oxygen as the acceptor for the addition of a vinylpalladium intermediate to achieve the cyclization. Oxazoline derivatives are generated as the Z-isomer with high
Iodine/Visible Light Photocatalysis for Activation of Alkynes for Electrophilic Cyclization Reactions
作者:Yuliang Liu、Bin Wang、Xiaofeng Qiao、Chen-Ho Tung、Yifeng Wang
DOI:10.1021/acscatal.7b00799
日期:2017.6.2
Photocatalytic organic synthesis needs photocatalysts to initiate the reactions and to control the reaction paths. Available photocatalytic systems rely on electron transfer or energy transfer between the photoexcited catalysts and the substrates. We explore a concept based on the photopromoted catalyst coupling to the substrate and the phototriggered catalyst regeneration by elimination from the catalytic
form, and which are otherwise impossible to access. Mechanistic evidence reveals the presence of an alkylgold intermediate, and an X‐ray crystal structure of the allylgold species illuminates its unique stability and reactivity. An asymmetric formal hetero‐enereaction of this gold intermediate, involving a dearomatization process, is enabled with assistance of a quinine‐derived squaramide catalyst. This
Synthesis of 2,2,2‐Trifluoroethyl Oxazoles, Oxazolines and Furans via Alkyne Oxytrifluoromethylation
作者:Jia‐Jia Dong、Song‐Lin Zhang
DOI:10.1002/adsc.201901405
日期:2020.2.21
This study reports an oxytrifluoromethylation method for construction of oxazoles and furans motif and the concurrent incorporation of a 2,2,2‐trifluoroethyl group at the aromatic C5‐position. High‐valent copper(III) trifluoromethyl compounds are crucial to this reaction that induces oxy‐trifluoromethylation of alkynes with a pendant amide/enol group functioning as the oxygen‐nucleophile. A wide substrate