Nucleophilicity of Alkyl Zirconocene and Titanocene Precatalysts, and Kinetics of Activation by Carbenium Ions and by B(C6F5)3

Berionni, Guillaume; Kurouchi, Hiroaki; Eisenburger, Lucien; Mayr, Herbert

doi:10.1002/chem.201602452

Cited by 9 publications

(2 citation statements)

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“…This is expected to be challenging, given the low nucleophilicity of these reagents. Notably, alkylzirconium compounds are reported to have a lower nucleophilicity than lithium boronates [ 16 ] (Scheme 1a). It might be the reduced s‐character (compared with sp‐ and sp 2 ‐hybridized organometallics), [ 17 ] and bulky ligands on the zirconium center render alkylzirconocenes more difficult to undergo transmetalation.…”

Section: Background and Originality Contentmentioning

confidence: 99%

Pd‐Catalyzed Cross‐Coupling of Alkylzirconocenes and Aryl Chlorides

Jiang

Shi

2022

Chin. J. Chem.

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Comprehensive Summary Alkylzirconocenes, readily prepared by hydrozirconation of alkenes with Schwartz's reagent, are perspective yet rarely exploited partners in transition‐metal catalyzed cross‐coupling reaction. The notoriously low nucleophilicity of alkylzirconocenes and the potential β‐H elimination restrict their application in cross‐coupling. Herein, we report the first Pd‐catalyzed aryl‐alkyl cross‐coupling of alkylzirconocenes and aryl halides. A commercially available N‐heterocyclic carbene (IPr) as the ligand for palladium catalyst is critical to enable the challenging process. This mild protocol does not require base additives and tolerates a broad scope of both coupling partners bearing various functional groups and heterocycles. Moreover, both terminal and internal alkenes are applicable, and the latter undergo “chain walking”, giving the terminal coupling product exclusively. Preliminary mechanistic studies reveal a precatalyst activation pathway and inhibited β‐H elimination due to steric bulk of NHC ligand.

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Section: Background and Originality Contentmentioning

confidence: 99%

Pd‐Catalyzed Cross‐Coupling of Alkylzirconocenes and Aryl Chlorides

Jiang

Shi

2022

Chin. J. Chem.

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“…Berionni and co-workers have measured the nucleophilicities of several representative organozirconium compounds. 28 Using Mayr's methodology, 29,30 the -nucleophilicities of various organozirconium compounds were determined via their reactions with benzhydrilium ions. The nucleophilicities (N) of these organozirconium compounds 4 were between 4.4 and 6.9.…”

Section: Scheme 3 Hydrozirconation Of Alkynesmentioning

confidence: 99%

Are Organozirconium Reagents Applicable in Current Organic Synthesis?

Némethová

Šebesta

2020

Synthesis

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The search for mild, user-friendly, easily accessible, and robust organometallic reagents is an important feature of organometallic chemistry. Ideally, new methodologies employing organometallics should be developed with respect to practical applications in syntheses of target compounds. In this short review, we investigate if organozirconium reagents can fulfill these criteria. Organozirconium compounds are typically generated via in situ hydrozirconation of alkenes or alkynes with the Schwartz reagent. Alkyl and alkenylzirconium reagents have proven to be convenient in conjugate additions, allylic substitutions, cross-coupling reactions, and additions to carbonyls or imines. Furthermore, the Schwartz reagent itself is a useful reducing agent for polar functional groups.1 Introduction2 Synthesis and Generation of the Schwartz Reagent3 Structure and Properties of Cp2Zr(H)Cl4 Reactivity of Organozirconium Reagents4.1 Asymmetric Conjugate Addition4.2 Asymmetric Allylic Alkylations4.3 Desymmetrization Reactions4.4 Cross-Coupling Reactions4.5 1,2-Additions5 Conclusions

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Hydrozirconation of Alkynes

Milligan,

Hammill,

Crocker

et al. 2023

Organic Reactions

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Since the first preparation of organozirconocenes from alkenes and alkynes in 1972, hydrozirconation has become one of the most commonly used stoichiometric methods to convert readily available starting materials into reactive but stable organometallic intermediates. A broad range of subsequent transformations may be employed to convert organozirconocenes in situ into high‐value functionalized products, often with the strategic formation of one (or several) new carbon–carbon bonds. This chapter focuses on the hydrozirconation of terminal and internal alkynes, and the subsequent synthetic transformations of the resulting alkenylzirconocenes. Zirconocene hydrochloride, Cp 2 Zr(H)Cl, is most frequently employed for the hydrozirconation step and can be used as a reagent or prepared in situ. Subsequent reactions of alkenylzirconocenes include additions to inorganic electrophiles such as halogens, as well as in situ ligand transfers to other metals, such as palladium and zinc, that further expand the range of accessible bond formations. The initial discussion focuses on the mechanism and stereochemical considerations, and on the steric and electronic factors that determine the regiochemistry of the either kinetically or thermodynamically controlled hydrozirconation. The “Scope and Limitations” section presents information on functional group compatibilities and is organized by the type of synthetic transformation of alkenylzirconocenes. Representative applications of the hydrozirconation of alkynes are showcased in syntheses of natural products, comparisons to alternative methods for the hydrometallation of alkynes. The goal of this chapter is to demonstrate the significance of hydrozirconation in organic synthesis, including the utility of the stoichiometric zirconium organometallics obtained from alkyne substrates, and to provide inspiration for the future development of new synthetic methods and strategies.

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Nucleophilicity of Alkyl Zirconocene and Titanocene Precatalysts, and Kinetics of Activation by Carbenium Ions and by B(C₆F₅)₃

Cited by 9 publications

References 56 publications

Pd‐Catalyzed Cross‐Coupling of Alkylzirconocenes and Aryl Chlorides

Pd‐Catalyzed Cross‐Coupling of Alkylzirconocenes and Aryl Chlorides

Are Organozirconium Reagents Applicable in Current Organic Synthesis?

Hydrozirconation of Alkynes

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