Selective carbon-carbon bond formation via transition metal catalysts. 9. Double metal catalysis in the cross-coupling reaction and its application to the stereo- and regioselective synthesis of trisubstituted olefins

Negishi, Ei‐ichi; Okukado, Nobuhisa; King, Anthony O.; Horn, David Van; Spiegel, Barry I.

doi:10.1021/ja00475a059

Cited by 306 publications

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“…S1 †). Furthermore, parallels exist to the bulky phosphinimide {μ-( t Bu) 3 PNAlCl 2 } 2 reported by Stephan and coworkers. 23 Interestingly, 2,6-dimethylimidazolin-2-imino aluminium dichloride VII, a less sterically congested derivative of 6, forms a six-membered Al 3 N 3 ring in the solid state in which most Alcentred bond angles nearly fit the ideal value of a tetrahedron (109.5°).…”

Section: 43mentioning

confidence: 59%

“…This indicates that the triflate substituents in 3 render the aluminium centres more electrophilic, thus strengthening the interaction with the nitrogen atoms of the adjacent ligands. While the replacement of one hydride at the aluminium atom for OTf − proceeded readily, we were not able to isolate a related species with a ditriflated metal centre even when treating {μ-LAlH 2 } 2 (2) with a large excess of Me 3 SiOTf at an elevated temperature.…”

Section: Dft Calculations Of Related Aluminium Dihydridesmentioning

confidence: 82%

“…The symmetric and asymmetric BH stretches of Al(BH 4 ) 3 have been reported at a comparable wavenumber. 53 In 46 Obviously, the J coupling between boron and hydrogen in 4 is not resolved.…”

mentioning

confidence: 82%

“…As for 4, the characteristic deviation of the 1 H and 13 C{ 1 H} NMR spectra of 7 (vide supra) is not reflected in its molecular structure in the solid state and, accordingly, strong similarities exist to the lower halide congeners 5 and 6. Precedence for the transformation of Al-H groups into Al-X functionalities (with X = Cl, Br or I) using BX 3 or Lewis base adducts thereof is scarcely found in the literature. To the best of our knowledge, the only related examples refer to the halogenation of Al-H moieties in carbaalane clusters employing the higher haloboranes.…”

Section: 43mentioning

confidence: 99%

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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: 43mentioning

confidence: 59%

Section: Dft Calculations Of Related Aluminium Dihydridesmentioning

confidence: 82%

“…The symmetric and asymmetric BH stretches of Al(BH 4 ) 3 have been reported at a comparable wavenumber. 53 In 46 Obviously, the J coupling between boron and hydrogen in 4 is not resolved.…”

mentioning

confidence: 82%

Section: 43mentioning

confidence: 99%

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

2014

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“…Electrophilic trapping is not limited to iodination: the intermediate organometallic reagent can participate in conjugate additions (entry 13), 8 allylation (entry 15), 9 stannylation (entry 16), and catalytic cross-coupling (entries 14, 17). 10,11 A series of experiments helped elucidate the effect of ZnCl 2 on the kinetics and thermodynamics of hydrozirconation. For example, in the absence of ZnCl 2 , hydrozirconation of the lithium alkoxide of 1a proceeds with moderate kinetic selectivity ( Table 3, entry 1) and little thermodynamic selectivity (entry 2).…”

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confidence: 99%

Directed Hydrozirconation of Propargylic Alcohols

Zhang

Ready

2007

J. Am. Chem. Soc.

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Hydrozirconation of terminal alkynes with Cp2ZrH(Cl) (Schwartz reagent) usually proceeds with high selectivity to yield the terminal vinyl zirconium. Under standard hydrozirconation conditions, terminal propargylic alcohols are no exception. However, we report that the sense of regioselectivity is completely reversed when the hydrozirconation is performed on the lithium alkoxide of terminal propargylic alcohols in the presence of ZnCl2. Only the more hindered, branched products are observed. The reaction tolerates silyl and alkyl ethers, aromatic and heteroaromatic rings, and even terminal olefins and alkynes. The intermediate vinyl organometallic reagent can be trapped with I2, enones, and allyl bromide and can participate directly in cross-coupling reactions. Products are isolated in good yields as single regioisomers. We provide evidence that the presence of ZnCl2 alters the kinetic selectivity such that the internal product is favored. More importantly, ZnCl2 inhibits isomerization of the vinyl metal species, likely through transmetalation to a vinyl zinc chloride.

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Totalsynthese von Makrolactin A über vielseitige katalytische, enantioselektive Dienolat-Aldoladditionen

1998

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Eine in hohem Maße konvergente Totalsynthese von Makrolactin A 1 wird vorgestellt, in der moderne Methoden zur asymmetrischen katalytischen C‐C‐Bindungsbildung eingesetzt werden. Die längste lineare Sequenz in dieser Synthese umfaßt 16 Schritte mit einer Durchschnittsausbeute von 86 % pro Schritt. Eine Totalsynthese von 1 ist unter anderem auch deshalb von Bedeutung, weil 1, das gegenüber HIV aktiv ist, nicht leicht aus seiner natürlichen Quelle, einem taxonomisch nicht klassifizierten Tiefsee‐Bakterium, in größerer Menge erhalten werden kann.

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Selective carbon-carbon bond formation via transition metal catalysts. 9. Double metal catalysis in the cross-coupling reaction and its application to the stereo- and regioselective synthesis of trisubstituted olefins

Cited by 306 publications

References 0 publications

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

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

Directed Hydrozirconation of Propargylic Alcohols

Totalsynthese von Makrolactin A über vielseitige katalytische, enantioselektive Dienolat-Aldoladditionen

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