Abstract
The bis-NHC–Ag/Pd(OAc)2 catalytic system (NHC = N-heterocyclic carbene), a combination of bis-NHC–Ag complex and Pd(OAc)2, was found to be a smart catalyst in the Pd-catalyzed transfer hydrogenation of various functionalized arenes and internal/terminal alkynes. The catalytic system demonstrated high efficiency for the reduction of a wide range of various functional groups such as carbonyls, alkynes, olefins, and nitro groups in good to excellent yields and high chemoselectivity for the reduction of functional groups. In addition, the protocol was successfully exploited to stereoselectivity for the transformation of alkynes to alkenes in aqueous media under air. This methodology successfully provided an alternative useful protocol for reducing various functional groups and a simple operational protocol for transfer hydrogenation.
Highlights
Metal-N-heterocyclic carbene (NHC) complexes possess a strong metal–carbene bond and these complexes play an important role in organometallic catalysis [1,2,3,4,5]
A dramatic drop in conversion was obtained in the absence of bis-NHC–Ag complex (8% conversion, entry 6), which means the bis-NHC–Ag/Pd(OAc)2 catalytic system raises the reactivity of the Pd metal center on the catalytic hydrogenation reaction
The synthesis of the bis-NHC–Ag complex was carried out according to our previous report [50]
Summary
Metal-N-heterocyclic carbene (NHC) complexes possess a strong metal–carbene bond and these complexes play an important role in organometallic catalysis [1,2,3,4,5] They have been developed into valuable catalytic systems in various reactions including Pd-catalyzed. Z/E ratio was displayed, the challenges are stillof functional group it is desirable to develop an alternative method for efficient transfer hydrogenation. NHC ligandsan were recently foundfor to efficient play antransfer important role in the it is hand, desirable to develop alternative method hydrosynthesis of the metallic nanoparticles (MNPs). NHC ligands were recently found to play an NPs) important the decomposition of Pd–NHC bonds in a Pd/NHC catalytic(Pd system or by the reduction in the synthesis of metallic nanoparticles.
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