Dehydrogenation of Diamine–Monoboranes to Cyclic Diaminoboranes: Efficient Ruthenium‐Catalyzed Dehydrogenative Cyclization

Wallis, Christopher J.; Dyer, Hellen; Vendier, Laure; Alcaraz, Gilles; Sabo-Étienne, Sylviane

doi:10.1002/anie.201108874

Cited by 34 publications

(36 citation statements)

References 48 publications

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“…The dehydrogenative cyclization of diaminemonoboranes has been reported to form cyclic diaminoboranes using a Ru(PCy 3 ) 2 (H 2 ) 2 (H) 2 catalyst; [23, 24] the metal-catalyzed dehydrocoupling of base-stabilised diborane(6) [H 2 B(hpp)] 2 to give [HB(hpp)] 2 (hpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) has been reported, alongside subsequent coordination chemistry; [25, 26] and there is an early report of sigma complexes formed from cyclic diboranes. [27] Shore and co-workers have developed the coordination chemistry and reactivity of related cyclic anionic organohydroborates of the early transition metals.…”

Section: Introductionmentioning

confidence: 99%

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

Kumar

Ishibashi

Hooper

et al. 2015

Chemistry A European J

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The coordination chemistry of the 1,2‐BN‐cyclohexanes 2,2‐R2‐1,2‐B,N‐C4H10 (R2=HH, MeH, Me2) with Ir and Rh metal fragments has been studied. This led to the solution (NMR spectroscopy) and solid‐state (X‐ray diffraction) characterization of [Ir(PCy3)2(H)2(η2η2‐H2BNR2C4H8)][BArF 4] (NR2=NH2, NMeH) and [Rh(iPr2PCH2CH2CH2PiPr2)(η2η2‐H2BNR2C4H8)][BArF 4] (NR2=NH2, NMeH, NMe2). For NR2=NH2 subsequent metal‐promoted, dehydrocoupling shows the eventual formation of the cyclic tricyclic borazine [BNC4H8]3, via amino‐borane and, tentatively characterized using DFT/GIAO chemical shift calculations, cycloborazane intermediates. For NR2=NMeH the final product is the cyclic amino‐borane HBNMeC4H8. The mechanism of dehydrogenation of 2,2‐H,Me‐1,2‐B,N‐C4H10 using the {Rh(iPr2PCH2CH2CH2PiPr2)}+ catalyst has been probed. Catalytic experiments indicate the rapid formation of a dimeric species, [Rh2(iPr2PCH2CH2CH2PiPr2)2H5][BArF 4]. Using the initial rate method starting from this dimer, a first‐order relationship to [amine‐borane], but half‐order to [Rh] is established, which is suggested to be due to a rapid dimer–monomer equilibrium operating.

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Section: Introductionmentioning

confidence: 99%

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

Kumar

Ishibashi

Hooper

et al. 2015

Chemistry A European J

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“…As reported in our previous communication, complex I serves as a precatalyst and is also identified as the catalyst resting state of the reaction,9 I being fully regenerated during the CDC process presumably as a result of evolution of dihydrogen. Despite the absence of observable intermediates,13 we speculated the reaction mechanism would involve the initial formation of a corresponding bis‐σ‐borane ruthenium complex with concomitant or subsequent creation of an interaction between the peripheral ending group and the bis‐σ‐coordinated borane moiety.…”

Section: Resultsmentioning

confidence: 55%

“…The X‐ray diffraction structure showed that the diamine backbone in D adopts an open chain structure without any interaction between the pendant NMe 2 group and the ligated borane moiety, in the solid state. However, the 1 H NMR study of D at room temperature in a [D 8 ]THF solution revealed the magnetic nonequivalence of the terminal hydrides ( δ= −11.94, −12.27 ppm) 9. This feature was not observed in the case of the previously reported complex [RuH 2 ((η 2 :η 2 ‐H 2 BNHMe)(PCy 3 ) 2 ]6 with two different substituents attached to the terminal nitrogen atom.…”

Section: Resultsmentioning

confidence: 80%

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A Highly Effective Ruthenium System for the Catalyzed Dehydrogenative Cyclization of Amine–Boranes to Cyclic Boranes under Mild Conditions

Wallis

Alcaraz

Petit

et al. 2015

Chemistry A European J

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We recently disclosed a new ruthenium-catalyzed dehydrogenative cyclization process (CDC) of diamine-monoboranes leading to cyclic diaminoboranes. In the present study, the CDC reaction has been successfully extended to a larger number of diamine-monoboranes (4-7) and to one amine-borane alcohol precursor (8). The corresponding NB(H)N- and NB(H)O-containing cyclic diaminoboranes (12-15) and oxazaborolidine (16) were obtained in good to high yields. Multiple substitution patterns on the starting amine-borane substrates were evaluated and the reaction was also performed with chiral substrates. Efforts have been spent to understand the mechanism of the ruthenium CDC process. In addition to a computational approach, a strategy enabling the kinetic discrimination on successive events of the catalytic process leading to the formation of the NB(H)N linkage was performed on the six-carbon chain diamine-monoborane 21 and completed with a (15) N NMR study. The long-life bis-σ-borane ruthenium intermediate 23 possessing a reactive NHMe ending was characterized in situ and proved to catalyze the dehydrogenative cyclization of 1, ascertaining that bis σ-borane ruthenium complexes are key intermediates in the CDC process.

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Dehydrocoupling and Other Cross‐couplings

Arrowsmith

2019

Early Main Group Metal Catalysis

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Dehydrogenation of Diamine–Monoboranes to Cyclic Diaminoboranes: Efficient Ruthenium‐Catalyzed Dehydrogenative Cyclization

Cited by 34 publications

References 48 publications

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

A Highly Effective Ruthenium System for the Catalyzed Dehydrogenative Cyclization of Amine–Boranes to Cyclic Boranes under Mild Conditions

Dehydrocoupling and Other Cross‐couplings

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