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

Abstract

M-HAT isomerization is a highly reliable method to access thermodynamically stable alkenes with high functional group tolerance. However, synthesis of heteroatom-substituted alkenes by M-HAT isomerization reaction is still underdeveloped. Herein, we report an enamide synthesis using M-HAT via a combination of cobalt and photoredox catalysis. This method tolerates a variety of functional groups including haloarenes, heteroarenes, free hydroxy groups, non-protected indoles, and drug derivatives. Furthermore, this method can isomerize styrene derivatives in good yield and E/Z selectivity.

A Neutral PCNHCP Co(I)–Me Pincer Complex as a Catalyst for N-Allylic Isomerization with a Broad Substrate Scope

“…Besides enamines, we were also interested if Co–Me could be used to isomerize N -allylamides, since the resulting enamides are extensively utilized in various organic transformations. ,, Although several methods are available for their synthesis, transition-metal-catalyzed isomerization is one of the most convenient and atom-economical routes. ,,− Consequently, we set out to test the isomerization of N -allylamides with our previous established reaction protocol (Table ). Gratifyingly, the isomerization of N -allyl- N -methylbenzamide proceeded readily at 80 °C and produced the corresponding enamide with excellent stereoselectivity (Table ; 6a ).…”

Photo‐ and Electrochemical Cobalt Catalysed Hydrogen Atom Transfer for the Hydrofunctionalisation of Alkenes

“…A similar silane‐free catalytic system has been used more recently by the same group for intramolecular hydroarylation to synthesise benzo‐fused δ‐lactams [72] . This catalytic platform has been further expanded very recently to the isomerisation of allylamides to polysubstituted enamides [73] …”

Metal free regio – and stereoselective semireduction of CF3-substituted N-allenamides

“…9 A combination of cobalt and photoredox catalysis was used to promote an isomerization by a hydrogen atom transfer to produce polysubstituted enamides (Scheme 1C). 10…”