A Stable Crystalline Carbene.
About: This article is published in ChemInform.The article was published on 1991-04-16. It has received 85 citations till now. The article focuses on the topics: Carbene.
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TL;DR: A concise overview of N-heterocyclic carbenes in modern chemistry is provided, summarizing their general properties and uses and highlighting how these features are being exploited in a selection of pioneering recent studies.
Abstract: The successful isolation and characterization of an N-heterocyclic carbene in 1991 opened up a new class of organic compounds for investigation. From these beginnings as academic curiosities, N-heterocyclic carbenes today rank among the most powerful tools in organic chemistry, with numerous applications in commercially important processes. Here we provide a concise overview of N-heterocyclic carbenes in modern chemistry, summarizing their general properties and uses and highlighting how these features are being exploited in a selection of pioneering recent studies.
2,932 citations
Cites background from "A Stable Crystalline Carbene."
...NHCs bearing alternative heteroatoms such as sulphur (3) and oxygen (4) are accessible, while stable carbenes containing only one nitrogen substituent, such as the series of cyclic (alkyl) (amino)carbenes (CAACs, 7) introduced by Bertrand et al....
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1,307 citations
TL;DR: The quest for stable carbenes is a long saga whose origin can be traced back to the first half of the 1800s as discussed by the authors, and the first stable crystalline carbene was reported in the early 1970s.
Abstract: A decade ago we initiated research, the goal of which was isolation of a stable carbene. Our success has helped to catalyze a resurgence of interest in readily available and easily handled carbenes. Research on stable (nucleophilic) carbenes is again a popular theme worldwide. Efforts in the general area of stable carbenes now focus not only on chemistry of the carbenes themselves but also on their applications to other chemical systems, where their chemical properties create technical opportunities that are unavailable with other functional groups. The quest for isolable carbenes is a long saga whose origin can be traced back to the first half of the 1800s. A recently published history of this quest provides an important backdrop for the research described in this Account.1 It is the intent of this Account to delineate the events and environment that led to the report from DuPont laboratories of the first isolation of a stable crystalline carbene. Getting Started
1,016 citations
TL;DR: Four main classes of NHC-containing palladium(II) complexes will be presented: palladium dimers with bridging halogens, palladacycles, palladium acetates and acetylacetonates, and finally pi-allyl complexes.
Abstract: Metal-catalyzed cross-coupling reactions, notably those permitting C−C bond formation, have witnessed a meteoritic development and are now routinely employed as a powerful synthetic tool both in academia and in industry. In this context, palladium is arguably the most studied transition metal, and tertiary phosphines occupy a preponderant place as ancillary ligands. Seriously challenging this situation, the use of N-heterocyclic carbenes (NHCs) as alternative ligands in palladium-catalyzed cross-coupling reactions is rapidly gaining in popularity. These two-electron donor ligands combine strong σ-donating properties with a shielding steric pattern that allows for both stabilization of the metal center and enhancement of its catalytic activity. As a result, the number of well-defined NHC-containing palladium(II) complexes is growing, and their use in coupling reactions is witnessing increasing interest. In this Account, we highlight the advantages of this family of palladium complexes and review their synt...
946 citations
TL;DR: This Account discusses another class of stable cyclic carbenes, namely, cyclic (alkyl)(amino)carbenes (CAACs), and shows that the peculiar electronic and steric properties of CAACs allow for the stabilization of unusual diamagnetic and paramagnetic main group element species.
Abstract: ConspectusCarbenes are compounds that feature a divalent carbon atom with only six electrons in its valence shell. In the singlet state, they possess a lone pair of electrons and a vacant orbital and therefore exhibit Lewis acidic and Lewis basic properties, which explains their very high reactivity. Following the preparation by our group in 1988 of the first representative, a variety of stable carbenes are now available, the most popular being the cyclic diaminocarbenes.In this Account, we discuss another class of stable cyclic carbenes, namely, cyclic (alkyl)(amino)carbenes (CAACs), in which one of the electronegative and π-donor amino substituents of diaminocarbenes is replaced by a σ-donating but not π-donating alkyl group. As a consequence, CAACs are more nucleophilic (σ-donating) but also more electrophilic (π-accepting) than diaminocarbenes. Additionally, the presence of a quaternary carbon in the position α to the carbene center provides steric environments that differentiate CAACs dramatically fr...
665 citations
References
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TL;DR: Synthese, structure et caracterisation du (1,3-bis [1-adamantyl]-2, 3-dihydro)-2,carbenoimidazole prepare par deprotonation du chlorure de (1 3-bis] [1]- imidazolium as discussed by the authors.
Abstract: Synthese, structure et caracterisation du (1,3-bis [1-adamantyl]-2,3-dihydro)-2-carbenoimidazole prepare par deprotonation du chlorure de (1,3-bis [1-adamantyl]) imidazolium
3,414 citations