Nickel‐Catalyzed Synthesis of Enamides and Enecarbamates via Isomerization of Allylamides and Allylcarbamates

Abstract

As ingle-component, air-stable nickel precatalyst can catalyzet he isomerization of allylamides for the synthesis of enamides.T he scope of the reactione ncompassesv arious substituted allylamides anda llylcarbamates as well as homoallylamides.T he reactionc an be performed on am ultigram-scale without specialized glove-box equipment or Schlenk techniques.Keywords: enamides; enecarbamates; homogeneous catalysis;i somerization;nickel catalysis Enamidesa nd enecarbamates are very useful synthetic intermediates for various transformations,s uch as cycloadditions,c ross-coupling reactions or asymmetric C À Cb ond formations (Scheme1). [1][2][3][4] Furthermore,e namidesa nd enecarbamatesa re valuable substrates for asymmetric hydrogenation reactions. [3,4] Besides these applications,t he enamide motif is often found in natural products,f or example,a spergillamides [5] and salicylihalamides [6] . Due to importance of these classeso fc ompounds, several protocols for theirp reparation have been reported.[1-4] Classical procedures,s uch as the acylation of imines or the condensation of amides and carbonyl compounds require harsh reactionc onditions and lead to the formation of considerable amounts of byproducts.[7] An attractivea lternative is the transition metal-catalyzed [8][9][10][11] or base-mediated [12] isomerization of readily available N-allylamides.R ecently,G ooßen and co-workersd eveloped as tereoselective synthesis of enamides based on ar uthenium-catalyzed direct addition of amides to terminala lkynes [13][14][15] . Foro ne of our current research projects,w ew ere looking for an operationally simple,s calable and effiScheme 1. Synthesis and applicationso fe namides.

Base-Metal-Catalyzed Olefin Isomerization Reactions

“…Instead of utilizing air-sensitive Ni(PPh 3 ) 4 , Manolikakes and co-workers found that air-stable Ni(II)-aryl complexes could be useful precatalysts for the isomerization of allyl amides (Scheme 18, eq 3). 40 This reaction system showed broad substrate scope, including allyl amides, allyl imides, allyl ureas, and allyl carbamates, as well as homoallylic amides.…”

"Syn-effect” in asymmetric vinylogous alkylation of 3-[4-(N-phthalimide)-but-2-enoyl]oxazolidinone

“…Some protocols are carried out under harsh reaction conditions, giving as reaction products mixtures of Z/E-enamides. [6][7][8][9][10][11][12][13][14] We report herein, the first asymmetric vinylogous alkylation of a chiral N-enoyl oxazolidinone, where the nitrogen atom is linked to the -unsaturated system as phthalimide group. This compound was treated under alkylation reaction conditions to give chiral Zenamides, -alkylated compounds bearing a double bond with a high Z-selectivity (> 98%).…”

Synthesis and crystal structures of two structurally related kryptoracemates

“…Recently, Halli et al (2017) published a modular two-step approach for the stereodivergent synthesis of 1,3-diamines (see Scheme 1). This approach is based on the reaction of an enamide (Halli, Kramer et al, 2015) with an insitu-formed N-acylimine (Halli, Hofman et al, 2015). The isolated intermediate can then react with a suitable nucleophile to set up three contiguous stereocentres.…”