Sterically Directed Functionalization of the Redox-Active Bis(imino)acenaphthene Ligand Class: An Experimental and Theoretical Investigation

Evans, D. A.; Vargas‐Baca, Ignacio; Cowley, Alan H.

doi:10.1021/ja407070y

Cited by 13 publications

(5 citation statements)

References 19 publications

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“…A similar alkyl transfer has also been observed in the reaction between n BuLi or MR 3 (M = group 13 metal, R = alkyl substituent) and I in noncoordinating solvents, leading to the formation of a imine-amido complex bearing an alkyl substituent on the carbon adjacent to the amide functionality . More recently Cowley and co-workers also reported the double alkylation of the acenaphthene backbone of I in the C 4 and C 5 positions by tert -butyllithium, via a radical dearomatization, two-electron reduction pathway, leading to the formation of complex V …”

Section: Introductionsupporting

confidence: 58%

“…While we have not fully rationalized the synthesis of this chiral, dimerized tetraimine product, we suggest its formation is possibly the result of a sterically induced radical coupling reminiscent of well-precedented reactivity observed for similarly redox inactive 4f-element complexes . In support of this hypothesis, Evans and Cowley have observed a radical anion C 5 -alkylated free radical as an intermediate in the formation of the dialkylated dearomatized lithium complex V …”

Section: Resultsmentioning

confidence: 68%

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Dearomatized BIAN Alkaline-Earth Alkyl Catalysts for the Intramolecular Hydroamination of Hindered Aminoalkenes

2013

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Reaction of a sterically encumbered bis(imino)acenapthene (dipp-BIAN) with either potassium alkyl or heavier alkaline earth dialkyl, [Ae{CH(SiMe 3 ) 2 } 2 (THF) 2 ] (Ae = Mg, Ca, Sr), reagents results in deromatization of the aromatic ligand. The heteroleptic alkaline earth alkyl species show enhanced stability toward Schlenk-type redistribution but undergo solution exchange when the bis(trimethylsilyl)methyl substituent is replaced by an anionic ligand of lower overall steric demands. In contrast analogous reactions performed with [Ba{CH(SiMe 3 ) 2 } 2 (THF) 2 ] evidenced facile solution redistribution and resulted in an unusual C-C coupling reaction which is suggested to result from a sterically induced reductive process. An assessment of the Mg, Ca, and Sr alkyl compounds as precatalysts for the intramolecular hydroamination of aminoalkenes evidenced enhanced reactivity which is ascribed to the greater solution stability of the catalytically active species. Most notably the calcium species may even be applied to the high yielding cyclization of substrates bearing alkyl substitution at either of the alkenyl positions.

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Section: Introductionsupporting

confidence: 58%

Section: Resultsmentioning

confidence: 68%

Dearomatized BIAN Alkaline-Earth Alkyl Catalysts for the Intramolecular Hydroamination of Hindered Aminoalkenes

2013

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“…A different type of addition to dpp‐bian was reported by Hill and co‐workers in 2011: the reactions of bulky organometallics, for example, K[CH(SiMe 3 ) 2 ] and M[CH(SiMe 3 ) 2 ] 2 (M=Mg, Ca, Sr), with dpp‐bian led to dearomatization of one of the six‐membered rings by addition of the nucleophile to the naphthalene ring . These processes were studied in detail by Cowley and co‐workers in 2013; they concluded that the functionalization of bians by organometallic species was sterically directed. Apparently, the formation of the complexes 7 and 19 are also sterically controlled processes.…”

Section: Resultsmentioning

confidence: 99%

Redox‐Active Ligand‐Assisted Two‐Electron Oxidative Addition to Gallium(II)

Fedushkin

Dodonov

Skatova

et al. 2018

Chemistry A European J

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The reaction of digallane (dpp-bian)Ga-Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η -All)Cl (3) and (dpp-bian)(Cl)Ga-Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η -All)Br (6) and (dpp-bian-All)(Br)Ga-Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph SnNCO afforded (dpp-bian)Ga(SnPh ) (8) and (dpp-bian)(NCO)Ga-Ga(NCO)(dpp-bian) (9). Treatment of GaCl with (dpp-bian)Na in diethyl ether resulted in the formation of (dpp-bian)GaCl (10). Diorganylgallium derivatives (dpp-bian)GaR (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp-bian)Ga(η -All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn GaCl, or tBu GaCl by salt metathesis. The salt elimination reaction between (dpp-bian)GaI (17) and tBuLi was accompanied by reduction of both the metal and the dpp-bian ligand, which resulted in digallane 2 as the final product. Similarly, the reaction of complex 10 with MentMgCl (Ment=menthyl) proceeded with reduction of the dpp-bian ligand to give the diamagnetic complex [(dpp-bian)GaCl ][Mg Cl (THF) ] (18). Compounds 11, 12, 13, 15, and 16 were thermally robust, whereas compound 14 decomposed when heated at reflux in toluene to give complex (dpp-bian-tBu)GatBu (19). Both complexes 7 and 19 contain R-substituted dpp-bian ligand: in the former compound the allyl group was attached to the imino-carbon atom, whereas in complex 19, the tBu group was situated on the naphthalene ring. Crystal structures of complexes 3, 8, 9, 10, 13, 14, 18, and 19 were determined by single-crystal X-ray analysis. The presence of dpp-bian radical anions in 3, 6, 8, and 10-16 was determined by ESR spectroscopy.

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“…Our initial attempt to decipher the mechanism using electron paramagnetic resonance (EPR) revealed that rather than a 3-electron reduction to generate an anionic Fe species, the formation of a radical anion of the ligand might be taking place. Radical dearomatization of dpp BIAN ligands in the presence of t -BuLi [148,149] and alkylation of dpp BIAN with n -BuLi due to the formation of organic radicals have been reported in the literature [150,151]. Titration of n -BuLi to a solution of dpp BIAN and dpp BIANFeCl 2 in toluene independently indicated a competition between ligand metathesis and complex reduction at each addition of n -BuLi (Scheme 9).…”

Section: Iron-catalyzed Hydrosilylationmentioning

confidence: 91%

Emergence and Applications of Base Metals (Fe, Co, and Ni) in Hydroboration and Hydrosilylation

Tamang

Findlater

2019

Molecules

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Base metal catalysis offers an alternative to reactions, which were once dominated by precious metals in hydrofunctionalization reactions. This review article details the development of some base metals (Fe, Co, and Ni) in the hydroboration and hydrosilylation reactions concomitant with a brief overview of recent advances in the field. Applications of both commercially available metal salts and well-defined metal complexes in catalysis and opportunities to further advance the field is discussed as well.

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Sterically Directed Functionalization of the Redox-Active Bis(imino)acenaphthene Ligand Class: An Experimental and Theoretical Investigation

Cited by 13 publications

References 19 publications

Dearomatized BIAN Alkaline-Earth Alkyl Catalysts for the Intramolecular Hydroamination of Hindered Aminoalkenes

Dearomatized BIAN Alkaline-Earth Alkyl Catalysts for the Intramolecular Hydroamination of Hindered Aminoalkenes

Redox‐Active Ligand‐Assisted Two‐Electron Oxidative Addition to Gallium(II)

Emergence and Applications of Base Metals (Fe, Co, and Ni) in Hydroboration and Hydrosilylation

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