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Review
. 2017 Jul 1;8(7):4688-4695.
doi: 10.1039/c7sc01657c. Epub 2017 May 24.

Cyclohexa-1,4-dienes in transition-metal-free ionic transfer processes

Sebastian Keess  1 , Martin Oestreich  1
Affiliations
Review

Cyclohexa-1,4-dienes in transition-metal-free ionic transfer processes

Sebastian Keess et al. Chem Sci. .

Abstract

Safe- and convenient-to-handle surrogates of hazardous chemicals are always in demand. Recently introduced cyclohexa-1,4-dienes with adequate substitution fulfil this role as El+/H- equivalents in B(C6F5)3-catalysed transfer reactions of El-H to π- and σ-donors (C[double bond, length as m-dash]C/C[triple bond, length as m-dash]C and C[double bond, length as m-dash]O/C[double bond, length as m-dash]N). Surrogates of Si-H/Ge-H, H-H and even C-H bonds have been designed and successfully applied to ionic transfer hydrosilylation/hydrogermylation, hydrogenation and hydro-tert-butylation, respectively. These processes and their basic principles are summarised in this Minireview. The similarities and differences between these transfer reactions as well as the challenges associated with these transformations are discussed.

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Figures

Scheme 1
Scheme 1. Reaction of cyclohexa-1,4-dienes with B(C6F5)3 in the absence (top) and presence (bottom) of π-basic substrates.
Fig. 1
Fig. 1. Substituted cyclohexa-1,4-dienes as synthetic equivalents of hydrosilanes/hydrogermanes (top), dihydrogen (middle) and isobutane (bottom).
Fig. 2
Fig. 2. Representative cyclohexa-1,4-dienes as surrogates of hydrosilanes (left) and hydrogermanes (right).
Scheme 2
Scheme 2. Transfer hydrosilylation and hydrogermylation of C–X multiple bonds using surrogates of Me3SiH and Et3GeH. a Performed at 90 °C.
Fig. 3
Fig. 3. Interplay between surrogate structure and reactivity. a Surrogate 1e fully consumed. b Partial deoxygenation to styrene.
Scheme 3
Scheme 3. Transfer hydrosilylation/hydrogermylation of alkenes with surrogates of monosilane or methylgermane. a Dicyclohexa-2,5-dien-1-ylsilane was used as the surrogate.
Scheme 4
Scheme 4. Gallium(iii)-assisted transfer hydrogenation of alkenes.
Scheme 5
Scheme 5. Gallium(iii)-assisted hydrogenative cyclisation of alkynes. a 2.4 equiv. of 3c used.
Scheme 6
Scheme 6. Catalytic cycles for Lewis and Brønsted acid-catalysed transfer hydrogenation of imines (X = NPG) and alkenes (X = CH).
Scheme 7
Scheme 7. Lewis and Brønsted acid-catalysed transfer hydrogenation of imines and nitrogen-containing heteroarenes. a Messy reaction. b 2.6 equiv. of surrogate 3a used. c Prepared by reductive amination.
Scheme 8
Scheme 8. Lewis acid- and Brønsted acid-catalysed transfer hydrogenation of alkenes.
Scheme 9
Scheme 9. Transfer hydro-tert-butylation of 1,1-diarylalkenes.
Scheme 10
Scheme 10. Proposed catalytic cycle for the transfer hydro-tert-butylation.
None
Sebastian Keess
None
Martin Oestreich
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References

    1. For a review, see: Wang D., Astruc D., Chem. Rev., 2015, 115 , 6621 –6686 . - PubMed

    1. For recent overviews of transition-metal-catalysed transfer processes, see:

    2. Bhawal B. N., Morandi B. Chem.–Eur. J. 2017;23 doi: 10.1002/chem.201605325. - DOI - PubMed
    3. Bhawal B. N., Morandi B. ACS Catal. 2016;6:7528–7535.

    1. For a review of transfer hydrosilylation, see:

    2. Oestreich M. Angew. Chem., Int. Ed. 2016;55:494–499. - PubMed
    3. Simonneau A., Oestreich M. Angew. Chem., Int. Ed. 2013;52:11905–11907. - PubMed
    4. Simonneau A., Friebel J., Oestreich M. Eur. J. Org. Chem. 2014:2077–2083.
    5. Keess S., Simonneau A., Oestreich M. Organometallics. 2015;34:790–799.
    6. Simonneau A., Oestreich M. Nat. Chem. 2015;7:816–822. - PubMed
    1. Keess S., Oestreich M. Org. Lett. 2017;19:1898–1901. - PubMed
    1. Chatterjee I., Oestreich M. Angew. Chem., Int. Ed. 2015;54:1965–1968. - PubMed
    2. Chatterjee I., Qu Z.-W., Grimme S., Oestreich M. Angew. Chem., Int. Ed. 2015;54:12158–12162. - PubMed
    3. Chatterjee I., Oestreich M. Org. Lett. 2016;18:2463–2466. - PubMed