Hydrodefluorination of non-activated C–F bonds by diisobutyl-aluminiumhydride via the aluminium cation [i-Bu2Al]+

Klahn, Marcus; Fischer, Christine; Spannenberg, Anke; Rosenthal, Uwe; Krossing, Ingo

doi:10.1016/j.tetlet.2007.10.056

Cited by 82 publications

(41 citation statements)

References 27 publications

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“…Several interesting quantities can be assessed by quantum‐chemical calculations, indicating the quality of an anion for a given task 18–20. The most important ones calculated as part of this work are:…”

Section: Resultsmentioning

confidence: 99%

Fluorinated Weakly Coordinating Anions [M(hfip)₆]^– (M = Nb, Ta): Syntheses, Structural Characterizations and Computations

Preiss

Steinfeld

Scherer

et al. 2013

Zeitschrift anorg allge chemie

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The synthesis, spectroscopic and structural characterisation of a series of [M(hfip)6]– (M = Nb, Ta; hfip = O–C(H)(CF3)2) salts that are the typical starting materials to introduce these weakly coordinating anions by metathesis reactions into a given system is described. The salts Li[Nb(hfip)6] and Li[Ta(hfip)6] formed in 65 to 77 % yield from freshly sublimed MCl5 and Li[hfip]. By contrast, several attempts to synthesize Li[Sb(hfip)6] on the similar route (replace NbCl5 by SbCl5) failed to yield a pure product. Upon metathesis of the Li‐niobate with AgF in CH2Cl2, the pure Ag[Nb(hfip)6] formed. Mixing Li[Nb(hfip)6] with an equimolar amount of Cl–CPh3 in CH2Cl2 gave the yellow [CPh3][Nb(hfip)6]. Several of the compounds were characterized by X‐ray analysis. Thus, the crystal structures of the Li+‐ and Ag+‐solvates 1, 2‐C6H4F2{LiNb(hfip)6}2, [Li(H2O)][Ta(hfip)6], and [Ag(C6H5F)][Nb(hfip)6] as well as that of [CPh3][Nb(hfip)6] were solved and are described in this work.

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Section: Resultsmentioning

confidence: 99%

Fluorinated Weakly Coordinating Anions [M(hfip)₆]^– (M = Nb, Ta): Syntheses, Structural Characterizations and Computations

Preiss

Steinfeld

Scherer

et al. 2013

Zeitschrift anorg allge chemie

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“…The group of Ozerov described, for example, the hydrodefluorination of C(sp 3 )−F bonds with electrophilic silylium species, for example, Et 3 Si + B(C 6 F 5 ) 4 − or Et 3 Si + [CHB 11 H 5 Cl 6 ] − . Similarly, Rosenthal, Krossing, and co‐workers postulated that the aluminum ion i Bu 2 Al + is the active catalyst (generated in situ from diisobutylaluminum hydride and a molecular activator, for example, Ph 3 C + B(C 6 F 5 ) 4 − ), in HDF of 1‐fluorohexane . Nicolau reported HDF of a glycosyl monofluoride with an equimolar amount of AlH 3 in diethylether .…”

Section: Introductionmentioning

confidence: 98%

Organocatalytic C−F Bond Activation with Alanes

Jaeger

Ehm

Lentz

2018

Chemistry A European J

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Hydrodefluorination reactions (HDF) of per- and polyfluorinated olefins and arenes by cheap aluminum alkyl hydrides in non-coordinating solvents can be catalyzed by O and N donors. TONs with respect to the organocatalysts of up to 87 have been observed. Depending on substrate and concentration, high selectivities can be achieved. For the prototypical hexafluoropropene, however, low selectivities are observed (E/Z≈2). DFT studies show that the preferred HDF mechanism for this substrate in the presence of donor solvents proceeds from the dimer Me Al (μ-H) ⋅THF by nucleophilic vinylic substitution (S V)-like transition states with low selectivity and without formation of an intermediate, not via hydrometallation or σ-bond metathesis. In the absence of donor solvents, hydrometallation is preferred but this is associated with inaccessibly high activation barriers at low temperatures. Donor solvents activate the aluminum hydride bond, lower the barrier for HDF significantly, and switch the product preference from Z to E. The exact nature of the donor has only a minimal influence on the selectivity at low concentrations, as the donor is located far away from the active center in the transition states. The mechanism changes at higher donor concentrations and proceeds from Me AlH⋅THF via S V and formation of a stable intermediate, from which elimination is unselective, which results in a loss of selectivity.

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“…Synthetic approaches toward difluoromethylated arenes. achieved by using electrochemical-, [13] aluminium-, [14] silylium- [15] and transition metal-based [16] protocols. Most of these methods, however, do not allow for the synthesis of difluoromethylated arenes because of the almost inevitable complete defluorination of the CF 3 group.…”

Section: Introductionmentioning

confidence: 99%

Selective Late‐Stage Hydrodefluorination of Trifluoromethylarenes: A Facile Access to Difluoromethylarenes

Munoz

Zhang

et al. 2017

Eur J Org Chem

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A selective reductive monodefluorination reaction of trifluoromethyl arenes was developed. Mediated by magnesium metal, various difluoromethylated aromatics were accessed at room temperature in the presence of acetic acid. This protocol shows tolerance to a wide range of functional groups and it was applicable in late‐stage hydrodefluorination of complex pharmaceutical compounds, affording the corresponding CF2H analogues and their deuterated (CF2D) counterparts.

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Hydrodefluorination of non-activated C–F bonds by diisobutyl-aluminiumhydride via the aluminium cation [i-Bu2Al]+

Cited by 82 publications

References 27 publications

Fluorinated Weakly Coordinating Anions [M(hfip)₆]^– (M = Nb, Ta): Syntheses, Structural Characterizations and Computations

Fluorinated Weakly Coordinating Anions [M(hfip)₆]^– (M = Nb, Ta): Syntheses, Structural Characterizations and Computations

Organocatalytic C−F Bond Activation with Alanes

Selective Late‐Stage Hydrodefluorination of Trifluoromethylarenes: A Facile Access to Difluoromethylarenes

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Hydrodefluorination of non-activated C–F bonds by diisobutyl-aluminiumhydride via the aluminium cation [i-Bu2Al]+

Cited by 82 publications

References 27 publications

Fluorinated Weakly Coordinating Anions [M(hfip)6]– (M = Nb, Ta): Syntheses, Structural Characterizations and ­Computations

Fluorinated Weakly Coordinating Anions [M(hfip)6]– (M = Nb, Ta): Syntheses, Structural Characterizations and ­Computations

Organocatalytic C−F Bond Activation with Alanes

Selective Late‐Stage Hydrodefluorination of Trifluoromethylarenes: A Facile Access to Difluoromethylarenes

Contact Info

Product

Resources

About

Fluorinated Weakly Coordinating Anions [M(hfip)₆]^– (M = Nb, Ta): Syntheses, Structural Characterizations and Computations

Fluorinated Weakly Coordinating Anions [M(hfip)₆]^– (M = Nb, Ta): Syntheses, Structural Characterizations and Computations