Iron‐Catalyzed Cyclotrimerization of Terminal Alkynes by Dual Catalyst Activation in the Absence of Reductants

Brenna, Davide; Villa, Matteo; Gieshoff, Tim N.; Fischer, Fabian; Hapke, Marko; Wangelin, Axel Jacobi von

doi:10.1002/ange.201705087

Cited by 17 publications

(8 citation statements)

References 50 publications

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“…This regioselectivity is close to that of the catalytic reaction using p-CH 3 C 6 H 4 C CH, but is distinct from that of von Wangelin's system that was proposed to have iron nanoparticles as the genuine catalyst. 42 With this limited information in hand, it is hard to determine whether this iron-catalyzed cyclotrimerization reaction oper-ates in a way of heterogeneous or homogeneous catalysis and further study is needed.…”

Section: For Comparisonmentioning

confidence: 85%

“…42 In the latter case, the iron particle was thought to be the genuine catalyst for the cyclotrimerization reaction. 42 The mechanism of the current iron-catalyzed alkyne cyclotrimerization reaction is not clear at this stage. Following the classical mechanism of low-valent transition-metalcatalyzed [2+2+2]-cycloaddition of alkynes, 43,44 we propose that the reaction catalyzed by 1 might start from the ligand substitution of vtms in 1 by alkynes to afford alkyne complex A.…”

Section: For Comparisonmentioning

confidence: 99%

“…41 It is also distinct from von Wangelin's system employing Fe(N(SiMe 3 ) 2 ) 2 as the precatalyst (100% and 98:2 selectivity for cyclotrimerization of p-CH 3 C 6 H 4 CCH and n-C 6 H 13 CCH, respectively). 42 In the latter case, the iron particle was thought to be the genuine catalyst for the cyclotrimerization reaction. 42 The mechanism of the current iron-catalyzed alkyne cyclotrimerization reaction is not clear at this stage.…”

Section: For Comparisonmentioning

confidence: 99%

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Three-Coordinate Iron(0) Complexes with N-Heterocyclic Carbene and Vinyltrimethylsilane Ligation: Synthesis, Characterization, and Ligand Substitution Reactions

et al. 2019

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Low-coordinate iron(0) species are implicated as intermediates in a range of iron-catalyzed organic transformations. Isolable iron(0) complexes with coordination numbers of less than four, however, are rarely known. In continuing with our interests in three-coordinate iron(0) complexes with N-heterocyclic carbene (NHC) and alkene ligation, we report herein the synthesis and ligand substitution reactivity of three-coordinate iron(0) complexes featuring monodentate alkene ligands, [(NHC)Fe(η 2 -vtms) 2 ] (vtms = vinyltrimethylsilane, NHC = 1,3bis(2′,6′-diisopropylphenyl)-imidazol-2-ylidene (IPr), 1; 1,3-bis(2′,6′-diisopropylphenyl)-4,5-tetramethylene-imidazol-2-ylidene (cyIPr), 2; 1,3-bis(2′,6′-diisopropylphenyl)-4,5,6,7-tetrahydro-1,3-diazepin-2-ylidene (7-IPr), 3). Complexes 1−3 were synthesized from the one-pot reactions of ferrous dihalides with the N-(2,6diisopropylphenyl)-substituted NHC ligands, vtms, and KC 8 . Reactivity study of 1 revealed its facile ligand substitution reactions with terminal aryl alkynes, ketones, isocyanides, and CO, by which iron(0) complexes [(IPr)Fe(η 2 -HCCAr)] (Ar = Ph, 5; p-CH 3 C 6 H 4 , 6; 3,5-(CF 3 ) 2 C 6 H 3 , 7), [(IPr)Fe(η 2 -OCPh 2 ) 2 ] (8), [(IPr)Fe(CNR) 4 ] (R = 2,6-Me 2 C 6 H 3 , 9; Bu t , 10), and (IPr)Fe(CO) 4 (11) were prepared in good yields. These iron(0) complexes have been characterized by 1 H NMR, solution magnetic susceptibility measurement, singlecrystal X-ray diffraction study, 57 Fe Mossbauer spectroscopy, and elemental analysis. Characterization data and computational studies suggest S = 1 ground-spin states for three-coordinate iron(0) complexes 1−3 and 5−8 and S = 0 ground states for 9− 11. Theoretical studies on the three-coordinate complexes 1, 6, and 8 indicated pronounced metal-to-ligand backdonation from occupied Fe 3d orbitals to the π* orbitals of the CC, CC, and CO moieties of the π ligands. In addition, 1 proved an effective precatalyst for the cyclotrimerization reaction of alkynes.

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Section: For Comparisonmentioning

confidence: 85%

Section: For Comparisonmentioning

confidence: 99%

Section: For Comparisonmentioning

confidence: 99%

See 1 more Smart Citation

Three-Coordinate Iron(0) Complexes with N-Heterocyclic Carbene and Vinyltrimethylsilane Ligation: Synthesis, Characterization, and Ligand Substitution Reactions

et al. 2019

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“…Nevertheless, oxabenzonorbornadiene was not suitable for present transformation mainly because of its higher activity, as only 1‐naphthalenol was generated by the cleavage of the C−O bond (Table , entry 7). The norbornene 1 i and mono‐substituted azabenzonorbornadiene 1 j failed to participate in the current [2+2] reaction, but the reaction gave cyclotrimerization product of 4‐methoxyphenylacetylene (Table , entries 8–9).…”

Section: Figurementioning

confidence: 99%

Nickel/Zinc Iodide Co‐catalytic Asymmetric [2+2] Cycloaddition Reactions of Azabenzonorbornadienes with Terminal Alkynes

Chen

et al. 2017

Adv Synth Catal

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The asymmetric [2 + 2] cycloaddition reactions of alkenes with alkynes are interesting as it has provided a powerful method for the construction of fused and strained cyclobutenes with multiple chiral centers. In this paper, we report the establishment of a dual catalysts system comprising nickel and zinc, which allowed the asymmetric [2 + 2] cycloaddition reactions of azabenzonorbornadienes with terminal alkynes in good yields and excellent enantioselectivities.Alkynes and alkenes are versatile building blocks in organic synthesis, and the transitional metal catalyzed reactions of alkynes and alkenes represent the diversity of organic reactions. To the reactions of bicyclic alkenes, the hydroalkynylation, [1] nucleophilic ringopening, [2] cycloaddition, [3] and some other reactions were well documented ( Figure 1). [4][5][6][7][8] Clearly, the development of new transitional metal catalyst system that with good chemoselectivity for the above mentioned reactions is of highly desirable and significant challenge. Among these reactions, the asymmetric [2 + 2] cycloaddition reaction seemed to be most intriguing as fused and strained cyclobutenes are generated with multiple chiral centers. The group of Cheng has taken the lead in the [2 + 2] cycloaddition reaction of bicyclic alkenes, [3a,c] and has first demonstrated the cycloaddition reaction of azabenzonorbornadiene with terminal alkyne, which featured the using of zinc powder to reduce the corresponding nickel or cobalt precursor, the synthetic application of the products were explored by ring-expansion to give cyclooctatetraene derivatives. By employing ruthenium catalyst, the group of Tam has further studied the scope of alkynes by using internal electron-deficient alkynes including alkynyl halides, alkynyl esters, and alkynyl phosphonates. [3b,9] In order to develop an asymmetric fashion, our group has used an iridium catalyst assisted by (R)-xylyl-Phanephos as chiral ligand, which has demonstrated excellent chiral control ability, but the reaction yields were generally moderate. [10] Recently, we have proved that using of Lewis acids were extremely effective to the activation of the aza-and oxa-bicyclic alkenes. [11] We envisioned that the similar co-catalyst system comprising a chiral nickel catalyst and Lewis acid could have a good performance in the asymmetric [2 + 2] cycloaddition reactions of azaben-Figure 1. Divergent reactions of heterobicyclic alkenes with alkynes (X=O or N-alkyl, R 1,2 = alkyl).

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“…Cyclotrimerization of alkynes is an effective method for the construction of polysubstituted benzene derivatives and an important cornerstone for the synthesis of new materials and bioactive compounds with high atomic economy [1–10] . Since the first proposal by Schweckendiek and Reppe for transition metal‐catalyzed trimerization of alkynes in 1948, [11] a variety of polysubstituted benzene derivatives have been achieved in the presence of Ru, [12–16] Rh, [17–22] or Pd [23–27] catalysts, among others [28–35] . Generally, the investigation is dominated by the transformation of terminal alkynes, [36–39] and the control of regioselectivity is still a bottleneck.…”

Section: Introductionmentioning

confidence: 99%

Ni‐Catalyzed Regioselective Cyclotrimerization of Internal Esteryl Alkynes towards Polysubstituted Benzene Rings

Hou

Ma²,

Zhang

et al. 2022

Helvetica Chimica Acta

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Transition‐metal‐catalyzed [2+2+2] cycloaddition of alkynes is a core synthetic approach to benzene rings. Herein we describe an efficient system based on inexpensive nickel catalyst and phosphine ligand that facilitate cyclotrimerization of various internal esteryl alkynes. The regioselectivity of the protocol was precisely controlled, and a series of polysubstituted benzene rings mainly composed of 1,2,4‐isomers were provided.

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Iron‐Catalyzed Cyclotrimerization of Terminal Alkynes by Dual Catalyst Activation in the Absence of Reductants

Cited by 17 publications

References 50 publications

Three-Coordinate Iron(0) Complexes with N-Heterocyclic Carbene and Vinyltrimethylsilane Ligation: Synthesis, Characterization, and Ligand Substitution Reactions

Three-Coordinate Iron(0) Complexes with N-Heterocyclic Carbene and Vinyltrimethylsilane Ligation: Synthesis, Characterization, and Ligand Substitution Reactions

Nickel/Zinc Iodide Co‐catalytic Asymmetric [2+2] Cycloaddition Reactions of Azabenzonorbornadienes with Terminal Alkynes

Ni‐Catalyzed Regioselective Cyclotrimerization of Internal Esteryl Alkynes towards Polysubstituted Benzene Rings

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