A Mild Method for Electrochemical Reduction of Heterocyclic <i>N</i>
-Oxides
作者:Yasuaki Fukazawa、Aleksandr E. Rubtsov、Andrei V. Malkov
DOI:10.1002/ejoc.202000377
日期:2020.6.16
heteroaromatic N-oxides is commonly accomplished using chemical or enzymatic methods. In this work, we report on an expedient protocol for electrochemical reduction of pyridine N-oxide derivatives under mild conditions. A diverse range of mono- and bis-N-oxides were converted into the corresponding nitrogen bases in good yields. Importantly, the method is highly selective towards N-oxides and tolerates
Functionalisation of quinoline N-oxide was investigated using phophazene base as a catalyst; alkynylation and heteroarylation at 2-position were successfully achieved via nucleophilic addition–elimination process.
Rh(III)-catalyzed switchable annulation of 2,2′-bipyridine N-oxides with internal alkynes via dual C–Hbondactivation has been developed. Tuning the reaction conditions enabled the reaction pathway to be switched between rollover and nonrollover annulation, delivering 5,6-disubstituted-1,10-phenanthrolines and 5,6,7,8-tetrasubstituted-1-(pyridin-2-yl)isoquinoline 2-oxides in high yields, respectively
An efficient potassium hydroxide‐catalyzed alkynylation of heteroaromatic N‐oxides under transition‐metal‐free conditions with the assistance of visible‐light has been developed. Various C2‐alkynylheterocycles were obtained in up to 92% yield with good functional group tolerance. This new method is operational simple, highly efficient, atom economic, and environmental friendly.