Cycloisomerization of 1,n-Enynes Via Carbophilic Activation

Toullec, Patrick Y.; Michelet, Véronique

doi:10.1007/128_2010_116

Cited by 79 publications

(18 citation statements)

References 193 publications

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“…The second investigated reaction is the Conia-ene cyclization of 2-cyano-hept-6-ynoate 20 to form 2-methylenecyclopentane 23 (Scheme ). , The Ni/Ag 2 complex 7-Ni provided nearly racemic product 23 in almost quantitative yield in the presence of ( i Pr) 2 NEt as a Brønsted base additive. In the absence of the base, only traces of product were found.…”

Section: Results and Discussionmentioning

confidence: 99%

Macrocyclic Salen–Bis-NHC Hybrid Ligands and Their Application to the Synthesis of Enantiopure Bi- and Trimetallic Complexes

2014

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Salen and NHC ligands are among the most important ligands for homogeneous catalysis. We have recently reported bimetallic complexes, in which both motifs have been merged for the first time. However, the intermetallic distances, which play a crucial role for cooperative bimetallic catalysis, were probably not appropriate in these first-generation hybrid catalysts. To generate heterobimetallic salen/NHC hybrid complexes with intermetallic distances suitable for cooperative catalysis, chiral macrocyclic hybrid ligands featuring a salen and two linked NHC donor moieties have been prepared in the present study. For the ligand formation, chiral enantiopure diamines as well as chiral enantiopure bisimidazoles were employed, and a matched/mismatched situation was found depending on the configuration of both chirality sources. Regioselective complexation of Zn(II), Ni(II), and Pd(II) by the salen N2O2 coordination sphere was efficiently accomplished. Subsequent coordination of the NHC units was achieved for Ag(I), Cu(I), Au(I), and Pd(II), in the latter case by oxidative transmetalation with Pd2(dba)3. X-ray crystal structure analyses for Ni/Ag2 and Pd/Ag2 complexes show strongly puckered macrocycles, in which one of the NHC-bound Ag(I) centers is in close proximity to the salen-bound Ni(II) or Pd(II) centers and in which this Ag(I) apparently interacts with both salen O-donor atoms. Preliminary data for the 1,4-addition of an oxindole to a nitroolefin and for the Conia-ene reaction of an α-cyanoacetate are reported.

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Section: Results and Discussionmentioning

confidence: 99%

Macrocyclic Salen–Bis-NHC Hybrid Ligands and Their Application to the Synthesis of Enantiopure Bi- and Trimetallic Complexes

2014

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“…It can be catalyzed by metal carbene complexes typically used for olefin metathesis (e.g., Grubbs-type catalysts, metallacyclobutene pathway, eq ), by oxidizable transition-metal complexes (metallacyclopentene pathway, eq ) or by transition- or main-group-based Lewis acids (outer sphere activation, eq ). , The mechanistic scenario is more complex in the latter case, as it involves many possible intermediates, some of them being either discrete energy minima in equilibrium, or resonance structures of a nonclassical carbocation . A common feature in eqs and 3 is the formation of a fused cyclobutene intermediate, which undergoes 4π conrotatory ring opening to give the final product (catalyzed by the Lewis acid or not).…”

Section: Introductionmentioning

confidence: 99%

Alkynophilicity of Group 13 MX₃ Salts: A Theoretical Study

et al. 2021

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The concept of alkynophilicity is revisited with group 13 MX 3 metal salts (M = In, Ga, Al, B; X = Cl, OTf) using M06-2X/6-31+G(d,p) calculations. This study aims at answering why some of these salts show reactivity toward enynes that is similar to that observed with late-transition-metal complexes, notably Au(I) species, and why some of them are inactive. For this purpose, the mechanism of the skeletal reorganization of 1,6-enynes into 1-vinylcyclopentenes has been computed, including monomeric ("standard") and dimeric (superelectrophilic) activation. Those results are confronted with deactivation pathways based on the dissociation of the M−X bond. The role of the X ligand in the stabilization of the intermediate nonclassical carbocation is revealed, and the whole features required to make a good π-Lewis acid are discussed.

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“…The group of Murai observed a similar reactivity in the presence of PtCl 2 , although in a lower yield [15]. These seminal contributions were then followed by several comprehensive studies involving carbophilic complexes such as platinum or gold [16–22] that led to the formation of complex bicyclic and tricyclic compounds [23–40]. The first asymmetric version was described by Shibata’s group in 2005 in the presence of a chiral iridium catalyst [41] (Scheme 1, reaction 2).…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

Pradal¹,

Chao²,

Toullec³

et al. 2011

Beilstein J. Org. Chem.

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SummaryA comprehensive study on the asymmetric gold-catalyzed cycloisomerization reaction of heteroatom tethered 1,6-enynes is described. The cycloisomerization reactions were conducted in the presence of the chiral cationic Au(I) catalyst consisting of (R)-4-MeO-3,5-(t-Bu)2-MeOBIPHEP-(AuCl)2 complex and silver salts (AgOTf or AgNTf2) in toluene under mild conditions to afford functionalized bicyclo[4.1.0]heptene derivatives. The reaction conditions were found to be highly substrate-dependent, the best results being obtained in the case of oxygen-tethered enynes. The formation of bicyclic derivatives, including cyclopropyl pentasubstituted ones, was reported in moderate to good yields and in enantiomeric excesses up to 99%.

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Cycloisomerization of 1,n-Enynes Via Carbophilic Activation

Cited by 79 publications

References 193 publications

Macrocyclic Salen–Bis-NHC Hybrid Ligands and Their Application to the Synthesis of Enantiopure Bi- and Trimetallic Complexes

Macrocyclic Salen–Bis-NHC Hybrid Ligands and Their Application to the Synthesis of Enantiopure Bi- and Trimetallic Complexes

Alkynophilicity of Group 13 MX₃ Salts: A Theoretical Study

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

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Cycloisomerization of 1,n-Enynes Via Carbophilic Activation

Cited by 79 publications

References 193 publications

Macrocyclic Salen–Bis-NHC Hybrid Ligands and Their Application to the Synthesis of Enantiopure Bi- and Trimetallic Complexes

Macrocyclic Salen–Bis-NHC Hybrid Ligands and Their Application to the Synthesis of Enantiopure Bi- and Trimetallic Complexes

Alkynophilicity of Group 13 MX3 Salts: A Theoretical Study

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

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Alkynophilicity of Group 13 MX₃ Salts: A Theoretical Study