Cobalt‐Catalyzed Chemoselective Isomerization of 2‐Substituted Allyl Ethers Induced by Hydrogen Atom Transfer

Abstract

A simple, mild and efficient method for the isomerization of 2‐substituted allyl ethers has been developed by cobalt‐catalyzed hydrogen atom transfer (HAT) process. The trivalent cobalt complex oxidized in‐situ by tert‐butyl hydroperoxide (tBuOOH) exhibits higher catalytic activity than prefabricated trivalent cobalt catalysts. This facile protocol displays excellent chemoselectivity, good functional group tolerance and high yields. The obtained vinyl ethers can be easily hydrolyzed by N‐iodosuccinimide/water to afford corresponding phenols or alcohols.

Synthesis of Polysubstituted Enamides by Hydrogen Atom Transfer Alkene Isomerization Using Dual Cobalt/Photoredox Catalysis

“…Chen also reported Z ‐selective enol ether synthesis from allyl ethers using a Co(salen) complex via M‐HAT and oxidative radical polar crossover [6] . Very recently, Li reported the chemoselective isomerization of 2‐substituted allyl ethers by M‐HAT [7] . However, the preparation of other heteroatom‐substituted alkenes using M‐HAT isomerization remains elusive.…”

“…[6] Very recently, Li reported the chemoselective isomerization of 2-substituted allyl ethers by M-HAT. [7] However, the preparation of other heteroatom-substituted alkenes using M-HAT isomerization remains elusive.…”

Ligand-controlled cobalt-catalyzed isomerization and reductive C–O bond cleavage of allylic ethers

“…Catalytic alkene isomerization is an efficient, straightforward, and atom-economical strategy to access regio- and stereodefined alkenes. 11 Employing this methodology, a number of metal catalysts based on iridium, 12 palladium, 13 ruthenium, 14 nickel 15 and cobalt 16 have been developed for the construction of enol ethers. However, these catalytic systems are mostly applicable to the synthesis of 1,2-disubstituted enol ethers (Scheme 1a).…”