Recent Advances and Perspectives in the Synthesis of HeterocyclesviaZinc Catalysis

Abstract

Among the various metal catalysts, zinc salts have enormous potential due to their availability, low toxicity, eco‐friendliness and inexpensive nature. Biologically zinc is an essential element in our daily lives and it possesses a wide range of applications in pharmaceutical as well as material sciences. In synthetic organic chemistry, the main role of zinc salts is as a Lewis acid catalyst. The importance of the synthesis of heterocycles is attested by the vast number of applications of these compounds in the chemical and pharmaceutical industries. The environmentally benign nature of zinc, its abundance and the Lewis acid character of most of its compounds make it a suitable catalyst for heterocycle synthesis. This is the first review exclusively on zinc‐catalyzed heterocycle synthesis and deals with the recent applications, especially using tandem/domino or one‐pot reaction strategies and covers the literature from 2008 to 2018.

Rhodium-Catalyzed Pyridine N-Oxide Assisted Suzuki–Miyaura Coupling Reaction via C(O)–C Bond Activation

“…However, the direct pyridine assisted ortho position C­(O)–C bond activation has not been reported, which might be caused by the difficulty in forming a stable four-membered ring intermediate (Scheme c). Meanwhile, pyridine N -oxides have been reported as activated starting substances for versatile derivations and also as the directing groups for selective C–H or C–C bond activation . In continuation of our work on C–H bond activation and C–C bond activation, herein is reported the development of a rhodium-catalyzed Suzuki–Miyaura-type coupling reaction of 2-benzoylpyridine N -oxides with boronic acids (Scheme c).…”

Asymmetric Zinc Catalysis in Green One-pot Processes

“…ZnEt 2 (10-20 mol%) 122 (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) In 2019, a bimetallic rhodium/zinc catalysis was employed by Shao et al to promote the first enantioselective domino ringopening/cyclopropanation reaction of oxabenzonorbornadienes 125 with phosphorus ylides 126 [71]. The dual catalysis involved a combination of 5 mol% of bis(1,5-cyclooctadiene)rhodium(I) tetrafluoroborate (Rh(cod) 2 BF 4 ), 50 mol% of Zn(OTf) 2 and 5.5 mol % of chiral biphosphine ligand 127.…”

“…Also in 2015 Lee and Bouffard reported the field of tandem reactions based on the use of organozinc reagents, albeit with no reference dealing with asymmetric zinc-catalyzed tandem reactions [21]. In 2019, a review on the synthesis of heterocycles via zinc catalysis was published by Beller and Anilkumar, including no reference concerning asymmetric work [22]. In 2020, Anilkumar reviewed zinc-catalyzed multicomponent reactions but with only one asymmetric work [23].…”

Rh(III)-Catalyzed C–H Bond Activation for the Construction of Heterocycles with sp3-Carbon Centers

“…Recently, many excellent reviews have summarized the construction of heterocycles by different transition-metal-catalyzed C-H activation were reported, such as Pd [29], Cu [30], Ru [31], Rh [32], Ag [33], and other metals [34][35][36][37][38]. However, to the best of our knowledge, there is currently no review focus on Rh(III)-catalyzed heterocyclic synthesis with sp 3 carbon centers.…”