Carbene Deprotonation
Carbene Deprotonation - Related Videos
10:44
Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
0 Views •
Cited by 5 •
2019
We present protocols for the isolation of stable heterocyclic carbenes. The synthesis of a cyclic (alkyl)(amino) carbene (CAAC) and an N-heterocyclic carbene (NHC) is demonstrated using filter cannulas and Schlenk technique. We furthermore present the synthesis of the related oxygen-sensitive, electron-rich mixed “Wanzlick dimer” and the reduced stable organic radical.
14:07
Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus
0 Views •
Cited by 2 •
2014
Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.
12:19
Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
0 Views •
Cited by 2 •
2018
We describe a protocol to photogenerate N-heterocyclic carbenes (NHCs) by UV irradiation of a 2-isopropylthioxanthone/imidazolium tetraphenylborate salt system. Methods to characterize the photoreleased NHC and elucidate the photochemical mechanism are proposed. The protocols for ring-opening metathesis photopolymerization in solution and miniemulsion illustrate the potential of this 2-component NHC photogenerating system.
19:58
Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
0 Views •
Cited by 1 •
2017
Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.
11:05
Quadruply Metal-Metal Bonded Paddlewheels
0 Views •
2023
Source: Corey Burns, Tamara M. Powers, Department of Chemistry, Texas A&M University Paddlewheel complexes are a class of compounds comprised of two metal ions (1st, 2nd, or 3rd row transition metals) held in proximity by four bridging ligands (most commonly formamidinates or carboxylates) (Figure 1). Varying the identity of the metal ion and the bridging ligand provides access to large families of paddlewheel complexes. The structure of paddlewheel complexes allows for metal-metal bonding,...
FAQs
The bonding electron pair from the removed C–H bond remains on the carbon atom rather than leaving with the proton. This converts the carbon center into a neutral carbene-bearing site and explains why the choice of precursor matters. A suitable precursor must contain a proton that can be removed while producing the desired stable or transient carbene.
The base must be sufficiently strong to remove the relevant acidic proton from the precursor. If proton removal is ineffective, carbene formation may not proceed adequately; if the reaction conditions are poorly matched to the precursor, the intended species may be difficult to generate or control. Base selection therefore directly influences whether the target carbene forms under the chosen conditions.
These conditions influence both formation and persistence of the carbene. Solvent and temperature must support proton removal and help manage whether the species remains stable or reacts quickly. Atmosphere is also critical because moisture and oxygen can react with highly reactive carbenes. Careful control of all three variables helps preserve the intended intermediate during preparation.
The outcome depends on the precursor and the surrounding reaction conditions. Some generated carbenes can persist long enough to be handled or used in subsequent chemistry, whereas others react rapidly after formation. This distinction determines whether the carbene is prepared as an isolable species or generated in situ for immediate use in a synthetic transformation.
A typical approach begins by selecting a suitable carbene precursor, such as an imidazolium salt, and a strong base capable of removing its acidic proton. The reaction is then conducted in an appropriately selected solvent at a controlled temperature and under a carefully managed atmosphere. These choices are coordinated to generate the desired carbene while limiting unwanted reactions with moisture or oxygen.
Deprotonation provides a route from suitable precursors, including imidazolium salts, to N-heterocyclic carbenes. Once generated, these species can serve as useful chemical tools rather than merely transient intermediates. Their preparation supports applications in organocatalysis and in the formation of metal-carbene complexes, making the method relevant to both catalyst development and synthetic chemistry.
Generated carbenes can function as organocatalysts, participate in the preparation of metal-carbene complexes, or serve as intermediates in synthetic transformations. The method is therefore valuable beyond the act of proton removal itself. Depending on whether the carbene is stable or transient, chemists can isolate it for later use or create it under controlled conditions for immediate reaction.