Allene formation by gold catalyzed cross-coupling of masked carbenes and vinylidenes

Lavallo, Vincent; Frey, Guido D.; Kousar, Shazia; Donnadieu, Bruno; Bertrand, Guy

doi:10.1073/pnas.0705809104

Cited by 278 publications

(170 citation statements)

References 42 publications

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“…Remarkably, abstraction of the metal-bound halide in 189 affords 190, which is a rare example of a stable arene Au + π-complex (see Scheme 65). 135 In an attempt to synthesize Grubbs-type catalysts featuring CAACs, the carbenes 191 were reacted with the Ru precursor complex 192 (see Scheme 66). 136 However, an unexpected air-sensitive product 193 was obtained, in which the phosphine rather than the pyridine was replaced by the carbene ligand.…”

Section: Coordination To Free Cyclic (Amino)(alkyl)carbenesmentioning

confidence: 99%

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

et al. 2009

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theme are found via the replacement or displacement of one N atom, thus providing carbenes derived from pyrazolium, isothiazolium, and even quinolinium salts that contain a stabilizing heteroatom in a remote position (G-J in Figure 1). Recently, carbenes such as K, which are comprised of only one heteroatom and lack delocalization through the heterocycle, have been discovered as versatile ligands, thus constituting another important class of carbenes with low heteroatom stabilization. Both the synthesis of the organometallic complexes of these ligands as well as the (catalytic) properties of the coordinated metal centers generally show distinct differences, compared to the more classical NHC complexes, such as C2-metallated imidazolylidenes. This review intends to describe such differences and highlights the chemical peculiarities of these types of N-heterocyclic carbene complexes. It introduces, in a qualitative manner, the synthetic routes that have been established for the preparation of such complexes, covering the literature from the very beginning of activities in this area up to 2008. While specialized reviews on some aspects of the present topic have recently appeared, 7 a comprehensive overview of the subject has not been available thus far. Rather than just being descriptive, the present account is mainly directed toward the impact of these still unusual metal-carbene bonding modes on the electronic properties and on the new catalytic applications that have been realized by employing such new carbene complexes. As a consequence of our focus on complexes with less-stabilized heterocyclic ligands, systems comprising acyclic carbenes have not been included, and the interested reader is, instead, referred to the pioneering and

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Section: Coordination To Free Cyclic (Amino)(alkyl)carbenesmentioning

confidence: 99%

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

et al. 2009

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“…[(CAAC)Au(PhMe)] + B(C 6 F 5 ) 4 − complexes are catalysts for the coupling of enamines and alkynes to yield allenes instead of propargyl compounds (Scheme 20) and thus to proceed differently as compared to the course of reactions with other catalysts [42,43].…”

Section: [(Nhc)au(solvent)]mentioning

confidence: 99%

“…Instead, the halide precursor [(CAAC)AuCl] can be treated with K[B(C 6 F 5 ) 4 ] in toluene to give the toluene solvate in which the solvent molecule is η 2 -π-bonded to the metal atom. In the original exploratory experiments this toluene complex was generated by applying the extremely powerful halide scavenger [(PhMe)SiEt 3 ] + B(C 6 F 5 ) 4 − , but later work has shown that this special reagent was not a prerequisite [42,43].…”

Section: [(Nhc)au(solvent)]mentioning

confidence: 99%

Silver-free Gold(I) Catalysts for Organic Transformations

Schmidbaur

Schier

2011

Zeitschrift Für Naturforschung B

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The majority of gold(I) catalysts employed in organic transformations in homogeneous systems are presently generated in situ by reactions of gold halides AuX or their 1 : 1 complexes [(L)AuX] with silver salts AgY (X = Cl, Br; L = R 3 P, NHC, tht etc.; Y = BF 4 , PF 6 , SbF 6 , OSO 2 CF 3 , OC(O)CF 3 etc.). This usage of silver salts is not only economically unfavorable, but also has several practical disadvantages regarding inter alia the thermal and photochemical stability of the reaction mixtures, problems of inexact stoichiometries, difficulties in separation and recycling, and cooperative effects due to Au-Ag metallophilic interactions which can induce a different course of the reactions. There is therefore a move towards syntheses of silver-free homogeneous gold(I) catalysts. The past and current approaches and opportunities are summarized in this review.

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“…6,10,11 The addition of a terminal alkyne to an activated enamine is the methodology of choice for the synthesis of racemic or chiral propargyl amines. [12][13][14] And the two processes can be catalyzed by the same metal catalyst (e.g., copper), so we proposed that the two processes be conducted in tandem: when a secondary amine attacks an intramolecularly tethered alkyne, the resulting activated enamine intermediate becomes a new electrophilic precursor capable of reacting with a second nucleophile, such as a terminal alkyne, to give a new addition product (Scheme 2-a). This tandem amination/alkynylation sequence will introduce an additional alkyne to the N-heterocycle, which can undergo further transformations (e.g., cycloisomerization).…”

Section: Introductionmentioning

confidence: 99%

“…103,104 Bertrand and coworkers generated cationic gold taking advantage of the high affinity of silica towards chloride (Scheme 18c). 105 Recently, Lafolle and Gandon reported the use of Cu(OTf)2 to activate L-AuCl. 106 The aforementioned non-silver activation methods have limitations.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of N-heterocycles through cyclization-triggered tandem additions to alkynes and the study of promoters in ionic reactions.

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Allene formation by gold catalyzed cross-coupling of masked carbenes and vinylidenes

Cited by 278 publications

References 42 publications

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

Silver-free Gold(I) Catalysts for Organic Transformations

Synthesis of N-heterocycles through cyclization-triggered tandem additions to alkynes and the study of promoters in ionic reactions.

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