Efficient and Selective Synthesis of (E)-Enamides via Ru(II)-Catalyzed Hydroamidation of Internal Alkynes

Abstract

An efficient hydroamidation of benzylamides with internal alkynes catalyzed by Ru­(II) has been developed. Various (E)-enamides were afforded in up to 95% yield for 28 examples. The protocol features excellent regio- and stereoselectivity, widely functional group tolerance, and easily accessible starting materials.

Silylium ion Migration Dominated Hydroamidation of Siloxy-alkynes

“…To date, the catalytic variant remains rather limited, especially in hydroamidation of internal alkynes [18][19][20] . To the best of our knowledge, there were only two hydroamidation reactions of internal alkyne which meet the requirements of atomic economic of ideal hydroamidation [18][19] .…”

“…To date, the catalytic variant remains rather limited, especially in hydroamidation of internal alkynes [18][19][20] . To the best of our knowledge, there were only two hydroamidation reactions of internal alkyne which meet the requirements of atomic economic of ideal hydroamidation [18][19] . Indisputably, make clear the mechanisms of these reactions are very important, for which can provide direct insights to broaden substrate scope and improve efficiency of such reaction.…”

“…In 2016, Cui et al reported first example of hydroamidation of phenyl-substituted alkyne with Ru(II) as catalyst 19 . The reaction proceed under relatively high temperature (90 ℃) and the substrates scope of amides is very limited, only the N1-benzyl-N2,N2-diisopropyloxalamide and its analogs are suitable for this reaction.…”

Synthesis of E/Z N‐(1‐Chlorovinyl)formamide Using Vilsmeier–Haack Reaction

“…N ‐Vinylformamides (NVFs), the simplest member of the enamide family, are stable enamide or enamine surrogates and have been endowed with fine physical and chemical characteristics which make them highly attractive on both commercial and scientific perspectives . In this context, various methods for the preparation of N ‐vinylenamide derivatives have been developed even to the commercial scale . Among these derivatives, α‐halo eneformamides are good substrates for α‐ and α,β‐functionalization to afford functionalized heterocycles via coupling reactions, which avoid the lability of the substrates under the coupling conditions .…”

Harnessing Stereospecific Z-Enamides through Silver-Free Cp*Rh(III) Catalysis by Using Isoxazoles as Masked Electrophiles

“…Unfortunately, these methods often lead to poor yields and scarce of E / Z selectivity and often require anhydrous as well as harsh reaction conditions (eminent temperature, strong base) . Although the synthetic strategy involving the metalation/functionalization of ynamides and the hydroamidation of alkynes had attracted chemists, these methods lacked broad substrate scope. Gold-catalyzed isomerization of propargylic alcohol (Meyer–Schuster rearrangement) and the isomerization of N -allyl amides under transition-metal catalysis could implement a diverse alternative to the coupling reactions.…”