ZrCl2(η-C5Me5)2-AlHCl2·(THF)2: efficient hydroalumination of terminal alkynes and cross-coupling of the derived alanes

Andrews, Philip S.; Latham, Christopher M.; Magre, Marc; Willcox, Darren; Woodward, Simon

doi:10.1039/c2cc37537k

Cited by 29 publications

(6 citation statements)

References 34 publications

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“…Furthermore, hydridoalanes are used in a diverse range of applications. For instance, the hydroalumination of carbonyl 1,2 and alkyne [3][4][5][6][7] functionalities is a common application for this class of compounds in organic synthesis. Though the intermediate aluminium species in these reactions are often elusive, the use of aluminium hydrides such as I 8 ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, characterization and reactivity of an imidazolin-2-iminato aluminium dihydride

2014

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The reaction of bis(2,6-diisopropylphenyl)imidazolin-2-imine (LH, 1) with Me 3 N·AlH 3 furnishes {μ-LAlH 2 } 2 (2). The marked tendency of 2 to release its hydride substituents is ascribed to the strong electron-donor character of the imidazolin-2-iminato ligand. This is supported by its reactivity study and DFT calculations.In fact, compound 2 was further converted with Me 3 SiOTf, Me 2 S·BH 3 , Me 2 S·BBr 3 , and BX 3 (with X = Cl, Br, and I) into {μ-LAl(H)OTf} 2 (3), {μ-LAl(BH 4 ) 2 } 2 (4), and {μ-LAlX 2 } 2 (5, X = Br; 6, X = Cl; 7, X = I), respectively.For all new aluminium complexes the formulation as dimers was evidenced by high resolution mass spectrometry, as well as single-crystal X-ray diffraction analysis. A prominent structural motif of these compounds is the square-planar four-membered Al 2 N 2 ring with two bridging bulky imidazolin-2-imino moieties. IntroductionAluminium hydrides -versatile reagents with rich chemistry For many years, chemical synthesis has been gaining immense benefit from the distinct reactivity of the aluminium-hydrogen bond. The strong need for highly selective transformations, increased focus on safety considerations, and efficiency in handling and storage are only some reasons why we find the chemically rogue parent aluminium hydride tamed into more suitable forms today. A variety of hydridoalanes has been tailored and very often reactivity adjustment is realized by steric congestion at the aluminium centre and by attaching strongly electron-donating substituents to the aluminium atom. Furthermore, hydridoalanes are used in a diverse range of applications. For instance, the hydroalumination of carbonyl 1,2 and alkyne 3-7 functionalities is a common application for this class of compounds in organic synthesis. Though the intermediate aluminium species in these reactions are often elusive, the use of aluminium hydrides such as I 8 ( Fig. 1) that bear highly sophisticated ligands grants access to all types of isolatable and well-defined model complexes. Compound I can be categorized as an aluminium dihydride and is related to the parent aluminium trihydride by replacement of one hydride for an anionic ligand. Thus, an ancillary ligand may be introduced, and yet, two reactive functional groups at the metal centre are preserved for the purpose of follow-up chemistry. The β-diketimino group, in particular, has been a key ligand to a rich chemistry of respective aluminium dihydrides. 9-12 A prominent example is II (Fig. 1), which can View Article OnlineView Journal | View Issue be used for the activation of non-polar element-element bonds as demonstrated by its conversion with elemental sulphur or selenium. 9,10 In a different field of applied science one finds chemical vapour deposition technology exploiting the thermodynamic properties of molecular aluminium hydrides for the purpose of creating composite materials. 1,13-15Aluminium hydrides are considered as fuel storagematerials with reasonable prospects in a hydrogen-based alternate energy-supply concept. 16,17 Moreover, the...

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Section: Introductionmentioning

confidence: 99%

Synthesis, characterization and reactivity of an imidazolin-2-iminato aluminium dihydride

2014

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“…6 The general procedure was followed with phenylacetylene (102.2 mg, 1.000 mmol) and 3iodotoluene (109.1 mg, 0.5000 mmol) for 24 h. Column chromatography (99/1 = hexane/EtOAc) afforded 3d as a colorless solid (87.4 mg, 90%): mp 42−43 °C; 1 H NMR (500 MHz, CDCl 3 ) δ 2.37 (s, 3 H, CH 3 ), 7.07−7.09 (m, 3 H), 7.24 (t, J = 7. 5 (125 MHz, CDCl 3 ) δ 21. 4, 123.7, 126.5, 127.2, 127.5, 128.4, 128.55, 128.6, 128.8, 137.2, 137.4, 138.2; LRMS (EI) m/z (% relative intensity) 194 (M + , 100), 179 (77), 115 (11), 96 (11), 89 (10).…”

Section: ■ Conclusionmentioning

confidence: 99%

“…Meanwhile, to the best of our knowledge, similar procedures that use a catalytic amount of a group 4 metal as the key catalyst have not yet been disclosed. Recently, Woodward et al have reported a palladium/zirconium-catalyzed reductive cross-coupling between alkynes and aryl halides that affords ( E )-alkenes . However, to effectively drive the corresponding coupling forward in this reaction, the addition of an excess of the key alkenyl aluminum intermediate, which is generated from alkynes and a dichloroalane–tetrahydrofuran complex (AlHCl 2 ·2THF), is necessary (Scheme a).…”

Section: Introductionmentioning

confidence: 99%

Group 4 Metallocene Difluoride/Palladium Bimetallic Catalysts for the Reductive Cross-Coupling of Alkynes with Aryl Iodides and Bromides

et al. 2018

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A novel protocol has been developed for the selective synthesis of (E)-alkenes via the reductive cross-coupling of alkynes and aryl halides using a bimetallic catalyst system composed of a group 4 metallocene difluoride (Cp2[M]F2; [M] = Hf or Zr; Cp = cyclopentadienide) and palladium dichloride. This reaction proceeds via a coupling between an aryl halide and an in situ generated alkenyl metallocene intermediate derived from the group 4 metallocene difluoride, a hydrosilane, and an alkyne. For a catalytic reductive coupling, the addition of sodium fluoride (NaF) to the reaction system is required. Moreover, in the presence of NaF, a ligand exchange was observed by NMR spectroscopy in hafnocene diiodide (Cp2HfI2) to afford hafnocene difluoride (Cp2HfF2).

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“…With the development of synthetic technology, various methods for obtaining trans -alkenes via alkyne reduction have emerged. The utilization of palladium, 6 nickel, 7 cobalt, 8 and other metals with the assistance of ligands is capable of reducing alkynes to trans -olefins using hydrogen or hydrogen surrogates (Scheme 1c), but these methods often require heating or high-pressure hydrogen gas, and the stereoselectivity and diversity of the reaction are not ideal. In comparison, trans -alkene products with excellent selectivity can be obtained by metal-catalyzed coupling reactions of alkynes with halogenated compounds.…”

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confidence: 99%

Highly stereoselective synthesis of trans-alkenes via electrochemical Ni-catalyzed hydroarylation of alkynes with aryl iodides

et al. 2023

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ZrCl2(η-C5Me5)2-AlHCl2·(THF)2: efficient hydroalumination of terminal alkynes and cross-coupling of the derived alanes

Cited by 29 publications

References 34 publications

Synthesis, characterization and reactivity of an imidazolin-2-iminato aluminium dihydride

Synthesis, characterization and reactivity of an imidazolin-2-iminato aluminium dihydride

Group 4 Metallocene Difluoride/Palladium Bimetallic Catalysts for the Reductive Cross-Coupling of Alkynes with Aryl Iodides and Bromides

Highly stereoselective synthesis of trans-alkenes via electrochemical Ni-catalyzed hydroarylation of alkynes with aryl iodides

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