Catalyst‐Free and Solvent‐Free Facile Hydroboration of Imines

Pandey, Vipin K; Donthireddy, S. N. R.; Rit, Arnab

doi:10.1002/asia.201901016

Cited by 38 publications

(27 citation statements)

References 55 publications

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“…aldehyde, 1 h, rt) 52 and should be taken into account when devising new catalysts for these transformations (Scheme 5). [52][53][54][55][56][57] Dilution of the reaction mixture reduces the yield of hydroboration. 55 Borohydrides are active catalysts for carbonyl hydroboration (e.g.…”

Section: B Hydroboration Of Carbonyl Derivativesmentioning

confidence: 99%

The Hidden Role of Boranes and Borohydrides in Hydroboration Catalysis

et al. 2020

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The continued development of hydroboration catalysts typifies the importance of this transformation as a testbed for catalytic activity and as a fundamental reaction for organic synthesis. Catalytic hydroboration studies routinely investigated the decomposition of HBcat but in the case of HBpin, decomposition is not commonly investigated due to its perceived stability.Organoboranes catalyze the hydroboration of alkenes and alkynes; these species can be formed

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Section: B Hydroboration Of Carbonyl Derivativesmentioning

confidence: 99%

The Hidden Role of Boranes and Borohydrides in Hydroboration Catalysis

et al. 2020

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“…(1), eg: N ‐(α‐methylbenzylidene)‐aniline, 1 a ); [8c] (2) Catalyst‐free hydroboration reaction of imine (Eq. (2), eg: N‐benzylideneaniline, 1 b ); [9] (3) BH 3 ⋅ SMe 2 ‐catalyzed hydroboration reaction of imine 1 b (Eq. (3), this work).…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insight into Hydroboration of Imines from Combined Computational and Experimental Studies

Zou

Gao

Cao

et al. 2022

Chemistry A European J

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Boron Lewis acid‐catalyzed and catalyst‐free hydroboration reactions of imines are attractive due to the mild reaction conditions. In this work, the mechanistic details of the hydroboration reactions of two different kinds of imines with pinacolborane (HBpin) are investigated by combining density functional theory calculations and some experimental studies. For the hydroboration reaction of N‐(α‐methylbenzylidene)aniline catalyzed by tris[3,5‐bis(trifluoromethyl)phenyl]borane (BArF3), our calculations show that the reaction proceeds through a boron Lewis acid‐promoted hydride transfer mechanism rather than the classical Lewis acid activation mechanism. For the catalyst‐ and solvent‐free hydroboration reaction of imine, N‐benzylideneaniline, our calculations and experimental studies indicate that this reaction is difficult to occur under the reaction conditions reported previously. With a combination of computational and experimental studies, we have established that the commercially available BH3 ⋅ SMe2 can serve as an efficient catalyst for the hydroboration reactions of N‐benzylideneaniline and similar imines. The hydroboration reactions catalyzed by BH3 ⋅ SMe2 are most likely to proceed through a hydroboration/B−H/B−N σ‐bond metathesis pathway, which is very different from that of the reaction catalyzed by BArF3.

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“…Quantitative substrate conversions with excellent chemoselectivities (>98%) were achieved with these particular imines, while, at the same time, generating the fastest reaction rates among the examined substrates, despite the transformations performing at −78 °C (for the selectivity purposes). Lastly, according to the results summarized in Table 1 , it appeared that this reduction protocol favored, in terms of reaction rates, ketimines over aldimines, which is not typically observed in the literature [ 10 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. At the moment, the precise reason(s) for this observation is(are) not known but it may suggest that the electrophilic step i.e., coordination of imine to BH 3 (see below) was rate determining, as one would expect that the hydride transfer (i.e., the nucleophilic step) would be less favored for ketimines over aldimines.…”

Section: Resultsmentioning

confidence: 73%

Imine Reduction with Me2S-BH3

et al. 2021

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Although there exists a variety of different catalysts for hydroboration of organic substrates such as aldehydes, ketones, imines, nitriles etc., recent evidence suggests that tetra-coordinate borohydride species, formed by activation, redistribution, or decomposition of boron reagents, are the true hydride donors. We then proposed that Me2S-BH3 could also act as a hydride donor for the reduction of various imines, as similar compounds have been observed to reduce carbonyl substrates. This boron reagent was shown to be an effective and chemoselective hydroboration reagent for a wide variety of imines.

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Catalyst‐Free and Solvent‐Free Facile Hydroboration of Imines

Cited by 38 publications

References 55 publications

The Hidden Role of Boranes and Borohydrides in Hydroboration Catalysis

The Hidden Role of Boranes and Borohydrides in Hydroboration Catalysis

Mechanistic Insight into Hydroboration of Imines from Combined Computational and Experimental Studies

Imine Reduction with Me2S-BH3

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