Scandium-Catalyzed Regio- and Stereospecific Methylalumination of Silyloxy/Alkoxy-Substituted Alkynes and Alkenes

Takimoto, Masanori; Usami, Saori; Hou, Zhaomin

doi:10.1021/ja909126k

Cited by 55 publications

(27 citation statements)

References 53 publications

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“…Analogously, the halfsandwich dialkylscandium complexes 2d-Sc and 2e-Sc in combination with [Ph 3 C][B(C 6 F 5 ) 4 ] could also serve as excellent catalysts for the regioselective methylalumination of alkenes having an alkoxy or siloxy tether group (Table 1). 36 In contrast to group-4 metal catalysts, with the scandium catalysts the alumination took place at the carbon atom proximal to the ether group and the methylation distal to the ether group, possibly because of the initial strong interaction between the electropositive scandium ion and the ether group. 36 The corresponding secondary alcohols were obtained in high yields upon oxidation of the resulting alkylaluminum species with O 2 ( Table 1).…”

Section: Methylalumination Of Alkenes and Alkynesmentioning

confidence: 99%

“…36 In contrast to group-4 metal catalysts, with the scandium catalysts the alumination took place at the carbon atom proximal to the ether group and the methylation distal to the ether group, possibly because of the initial strong interaction between the electropositive scandium ion and the ether group. 36 The corresponding secondary alcohols were obtained in high yields upon oxidation of the resulting alkylaluminum species with O 2 ( Table 1).…”

Section: Methylalumination Of Alkenes and Alkynesmentioning

confidence: 99%

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Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

2015

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The search for new catalysts for more efficient, selective chemical transformations and for the synthesis of new functional materials has been a long-standing research subject in both academia and industry. To develop new generations of catalysts that are superior or complementary to the existing ones, exploring the potential of untapped elements is an important strategy. Rare-earth elements, including scandium, yttrium, and the lanthanides (La-Lu), constitute one important frontier in the periodic table. Rare-earth elements possess unique chemical and physical properties that are different from those of main-group and late-transition metals. The development of rare-earth-based catalysts by taking the advantage of these unique properties is of great interest and importance. The most stable oxidation state of rare-earth metals is 3+, which is difficult to change under many reaction conditions. The oxidative addition and reductive elimination processes often observed in catalytic cycles involving late transition metals are generally difficult in the case of rare-earth complexes. The 18-electron rule that is applicable to late-transition-metal complexes does not fit rare-earth complexes, whose structures are mainly governed by the sterics (rather than the electron numbers) of the ligands. In the lanthanide series (La-Lu), the ionic radius gradually decreases with increasing atomic number because of the influence of the 4f electrons, which show poor shielding of nuclear charge. Rare-earth metal ions generally show strong Lewis acidity and oxophilicity. Rare-earth metal alkyl and hydride species are highly reactive, showing both nucleophilicity and basicity. The combination of these features, such as the strong nucleophilicity and moderate basicity of the alkyl and hydride species and the high stability, strong Lewis acidity, and unsaturated C-C bond affinity of the 3+ metal ions, can make rare-earth metals unique candidates for the formation of excellent single-site catalysts. This Account is intended to give an overview of our recent studies on organo rare-earth catalysis, in particular the synthesis and application of half-sandwich rare-earth alkyl complexes bearing monocyclopentadienyl ligands for olefin polymerization, carbometalation, and hydroarylation. Treatment of half-sandwich rare-earth dialkyl complexes having the general formula CpMR2 with an equimolar amount of an appropriate borate compound such as [Ph3C][B(C6F5)4] can generate the corresponding cationic monoalkyl species, which serve as excellent single-site catalysts for the polymerization and copolymerization of a wide range of olefin monomers such as ethylene, 1-hexene, styrene, conjugated and nonconjugated dienes, and cyclic olefins. The cationic half-sandwich rare-earth alkyl complexes can also catalyze the regio- and stereoselective alkylative alumination of alkenes and alkynes through insertion of the unsaturated C-C bond into the metal-alkyl bond followed by transmetalation between the resulting new alkyl or alkenyl species and an alkylaluminum...

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Section: Methylalumination Of Alkenes and Alkynesmentioning

confidence: 99%

Section: Methylalumination Of Alkenes and Alkynesmentioning

confidence: 99%

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

2015

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“…5 (C) The Cu-catalyzed enantioselective conjugate addition of a β-alkenylalkylaluminium reagent (prepared via Ni catalysis) to an α,β-unsaturated ketone (which is issued by Zr-catalyzed carboalumination using TMA) was reported by McGrath and Hoveyda. 6 This multicomponent reaction allowed the enantioselective synthesis of β,β-disubstituted ketones from alkynes.…”

Section: Table 1 Use Of Trimethylaluminiummentioning

confidence: 99%

Trimethylaluminium

Drissi-Amraoui

2015

Synlett

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Sammy Drissi-Amraoui was born in Bressuire, France in 1990. In 2011, he worked as a oneyear student in the Chemistry Department of Merck Serono, Geneva, under the supervision of Dr. Cyril Montagne and Dr. Dominique Swinnen, working on photochemistry for the synthesis of drug-like compounds. In 2013, he graduated from the Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM) in organic chemistry and received his M.Sc. in chemistry of biomolecules for health. He started his Ph.D. studies in 2013 under the supervision of Prof. Jean-Marc Campagne and Dr. Renata Marcia de Figueiredo and his research focuses on asymmetric conjugate additions and total synthesis.

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“…External THF ligands would continuously coordinate to the metal site and seriously hinder the polymerization reaction. Similar Cp'Sc(DMA) 2 (6) complexes have been used as catalysts for the carboalumination of alkoxy substituted alkynes or alkenes and display unique regio-and stereoselectivity [31].…”

Section: Conversions and Applicationsmentioning

confidence: 99%

Benzyllanthanide Chemistry: Revival of Manzer’s ortho‐Me₂N‐Benzyl Ligand

Harder¹

2010

Zeitschrift anorg allge chemie

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The Manzer benzyl ligand, ortho-Me 2 N-benzyl (DMA), has been introduced in lanthanide (Ln) chemistry more than three decades ago with the syntheses of Sc(DMA) 3 and Er(DMA) 3 but no reaction chemistry or structures have been described. Only recently it was shown that a Ln(DMA) 3 complex can also be obtained for the largest Ln metal La and first crystal structures appeared. At present crystal structures of many Ln(DMA) 3 complexes throughout the series have been determined and were found to be isomorphous. This reports describes the improvement of synthetic methods for Ln(DMA) 3 complexes, a discussion on structures and trends and more important, the wide scope of Ln(DMA) 3 reagents as versatile building-blocks in lanthanide chemistry: the fast-growing number of complexes and catalysts that have been made starting from a Ln(DMA) 3 reagent are summarized. Despite the intramolecular chelating Me 2 N-arm, half-sandwich catalysts containing the DMA fragment are still active in alkene polymerizations or other catalytic conversions. The main advantages of Ln(DMA) 3 complexes are: i) easy syntheses from commercially available starting materials, ii) convenient crystallization which warrants high purity, iii) high stability on account of intramolecular coordination while sufficient reactivity for further conversions is maintained and iv) availability of these reagents over the full Ln range which is advantageous for catalyst screening.

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Scandium-Catalyzed Regio- and Stereospecific Methylalumination of Silyloxy/Alkoxy-Substituted Alkynes and Alkenes

Cited by 55 publications

References 53 publications

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

Trimethylaluminium

Benzyllanthanide Chemistry: Revival of Manzer’s ortho‐Me₂N‐Benzyl Ligand

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Scandium-Catalyzed Regio- and Stereospecific Methylalumination of Silyloxy/Alkoxy-Substituted Alkynes and Alkenes

Cited by 55 publications

References 53 publications

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

Trimethylaluminium

Benzyllanthanide Chemistry: Revival of Manzer’s ortho‐Me2N‐Benzyl Ligand

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Benzyllanthanide Chemistry: Revival of Manzer’s ortho‐Me₂N‐Benzyl Ligand