(Pentamethylcyclopentadienyl)rhodium (RhCp*)‐catalyzed CH transformations have emerged as a prosperous field in CH bond activation. Recent advances in this area have significantly focused on the ...development of new strategies for CC and Cheteroatom bond formation that are characterized by the novel reactivity of the RhCp* catalyst to undergo formal SN‐type reactions with electrophilic substrates. This review is intended to give an overview on this rather new class of RhCp*‐catalyzed CH transformations, covering recent CC and Cheteroatom bond‐forming reactions. The nature of the reaction partner in these CH functionalization reactions serves as a guideline throughout this article and, combined with selected descriptions of mechanistic proposals, should emphasize general characteristics of transformations within this novel reaction class.
A copper‐catalyzed reductive cross‐coupling reaction of nonactivated alkyl tosylates and mesylates with alkyl and aryl bromides was developed. It provides a practical method for efficient and ...cost‐effective construction of aryl–alkyl and alkyl–alkyl CC bonds with stereocontrol from readily available substrates. When used in an intramolecular fashion, the reaction enables convenient access to various substituted carbo‐ or heterocycles, such as 2,3‐dihydrobenzofuran and benzochromene derivatives.
CC bond formation: A copper‐catalyzed reductive cross‐coupling reaction of nonactivated alkyl tosylates and mesylates with alkyl and aryl bromides was developed. This reaction can be used to construct aryl–alkyl and alkyl–alkyl CC bonds with stereocontrol from readily available substrates. Intramolecular cyclization reactions also enable access to various substituted 2,3‐dihydrobenzofuran and benzochromene derivatives.
Palladium‐catalyzed coupling reactions have become a central tool for the synthesis of biologically active compounds both in academia and industry. Most of these transformations make use of easily ...available substrates and allow for a shorter and more selective preparation of substituted arenes and heteroarenes compared to non‐catalytic pathways. Notably, molecular‐defined palladium catalysts offer high chemoselectivity and broad functional group tolerance. Considering these advantages, it is not surprising that several palladium‐catalyzed coupling reactions have been implemented in the last decade into the industrial manufacture of pharmaceuticals and fine chemicals. In this review different examples from 2001–2008 are highlighted, which have been performed at least on a kilogram scale in the chemical and pharmaceutical industries.
All(yl) possible! A rhodium(III)‐catalyzed intermolecular direct CH allylation reaction utilizing readily accessible allyl carbonates was developed. This method allows the allylation of ...electron‐neutral arenes, providing complete γ‐selectivity, high isomeric ratio, good substrate scope, and excellent functional group compatibility.
Carbon‐carbon bond formation is among the most challenging transformations in the organic synthetic chemistry. Enzymes capable to perform this reaction are of great interest. The enzymes for ...stereoselective CC bond formations have been investigated very intensively during the last two decades. New recombinant DNA technologies have paved the way for improved catalysts and broaden the application scope of the already known enzymes and reactions. On the other side new discoveries have brought more enzyme players in the arena of CC bond formation reactions. Novel enzymatic CC bond formation reactions have been applied, implying the most important benefit of biocatalysis, namely the high selectivity.
One plus One makes One: This review describes the latest results regarding optimizations and applications of the novel as well as known enzymes for carbon‐carbon bond formation.
This account provides a comprehensive overview of the development of gold and platinum catalysis of the enyne cycloisomerization. The use of these soft, alkynophilic metals enables mild, ...chemoselective and efficient transformations of a variety of readily available acyclic enynes to a wide range of synthetically useful carbocyclic and heterocyclic products. The review is organized according to diverse structural types of enynes that undergo skeletal cycloisomerizations. The account begins with an overview of transformations of primarily 1,6‐enynes to 1‐alkenylcyclopentenes, bicyclo4.1.0heptenes, methylenecycloalkenes, bicyclo4.3.0nonadienes and bicyclo3.2.0heptenes. This section is followed by the discussion of cycloisomerizations of 1,5‐enynes, which enable a rapid access to a range of other cyclic products, including bicyclo3.1.0hexenes, cyclohexadienes, heterobicycloalkenes, methylenecyclopentenes, naphthalenes and methyleneindenes. In addition, the 3,3 rearrangement of 1,5‐enynes provides efficient access to the corresponding allenes. The account concludes with an overview of the most recent studies on gold‐ and platinum‐catalyzed cycloisomerizations of 1,4‐ and 1,3‐enynes. Due to the rapidly increasing interest in this area during the past three to five years, we believe that this review provides a timely and comprehensive discussion of the development gold‐ and platinum‐catalyzed cycloisomerization starting from the initial pioneering investigations to the latest advances in the field. A significant emphasis is placed on the mechanistic discussion of the observed manifolds of skeletal reorganizations.
In the recent years, significant progress has been made toward designing active and selective catalysts for electrochemical CO2 reduction, with particular interest focused on the two major C2 ...productsethylene and ethanol. Numerous efforts have been made to enhance the understanding of the heterogeneous copper-based CO2 reduction mechanisms by computational studies. Here we provide a critical assessment of various proposed scenarios of the initial and post C–C coupling steps that result in either ethylene or ethanol. In silico rationalization of the parameters controlling the product selectivity, such as the catalyst structure and composition (Cu facets, the presence of defective sites and/or subsurface oxygen atoms, or the interplay with a second metal) and the reaction conditions (pH, applied potential, and electrolyte), is provided. A comprehensive scheme combining the proposed pathways is derived, and the issues that are still under debate and require further investigations are highlighted.
Herein we describe the enantioselective intermolecular conjugate addition of nitroalkanes to unactivated α,β‐unsaturated esters, catalyzed by a bifunctional iminophosphorane (BIMP) superbase. The ...transformation provides the most direct access to pharmaceutically relevant enantioenriched γ‐nitroesters, utilizing feedstock chemicals, with unprecedented selectivity. The methodology exhibits a broad substrate scope, including β‐(fluoro)alkyl, aryl and heteroaryl substituted electrophiles, and was successfully applied on a gram scale with reduced catalyst loading, and, additionally, catalyst recovery was carried out. The formal synthesis of a range of drug molecules, and an enantioselective synthesis of (S)‐rolipram were achieved. Additionally, computational studies revealed key reaction intermediates and transition state structures, and provided rationale for high enantioselectivities, in good agreement with experimental results.
The first intermolecular enantioselective addition of nitroalkanes to unactivated α,β‐unsaturated esters is described, catalyzed by a bifunctional iminophosphorane (BIMP) superbase. This fundamental synthetically relevant transformation proceeds with high enantiomeric excesses and yields over a wide range of feedstock substrates, providing pharmaceutically relevant building blocks in a single step.
An overview of recent progress in the Fujiwara–Moritani reaction, which is the palladium‐catalyzed oxidative coupling of arenes with olefins to afford alkenyl arenes, is described. It is emphasized ...that regioselectivity on aryl ortho‐ or meta‐CH activation could be controlled very well in the presence of Pd, Rh, or Ru catalysts with the assistance of various chelation groups on aromatic rings in this coupling reaction. Catalytic alkenylation of aryl CH bonds from simple arenes is also discussed, especially from electron‐deficient arenes. These advanced protocols would not only make the Fujiwara–Moritani reaction more useful and applicable in organic synthesis but also light the way for the further development of the functionalization of normal CH bonds.
Chemical power tools: The Fujiwara–Moritani reaction is the palladium‐catalyzed coupling reaction of a simple aryl CH bond with an alkenyl CH bond to form a new CC bond (see scheme). This Minireview focuses on the advances in the past five years related to the activation of various aryl CH bonds in this coupling reaction.
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