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. 2021 Jul 12;60(29):16035-16043.
doi: 10.1002/anie.202103550. Epub 2021 Jun 9.

Manganese-Catalyzed Hydroborations with Broad Scope

Pradip Ghosh  1 , Axel Jacobi von Wangelin  1
Affiliations

Manganese-Catalyzed Hydroborations with Broad Scope

Pradip Ghosh et al. Angew Chem Int Ed Engl. .

Abstract

Reductive transformations of easily available oxidized matter are at the heart of synthetic manipulation and chemical valorization. The applications of catalytic hydrofunctionalization benefit from the use of liquid reducing agents and operationally facile setups. Metal-catalyzed hydroborations provide a highly prolific platform for reductive valorizations of stable C=X electrophiles. Here, we report an especially facile, broad-scope reduction of various functions including carbonyls, carboxylates, pyridines, carbodiimides, and carbonates under very mild conditions with the inexpensive pre-catalyst Mn(hmds)2 . The reaction could be successfully applied to depolymerizations.

Keywords: amides; carbon dioxide; carbonates; depolymerization; hydroboration; manganese.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Top: Catalytic hydroborations of polar substrates as a key strategy of reduction and valorization. Center: Recently reported Mn catalysts for C=X hydroborations. Bottom: Lipophilic and basic metal‐hmds salts as inexpensive catalysts for C=X hydroborations.
Scheme 2
Scheme 2
Synthesis of various metal hexamethyldisilazides, M(hmds)1–2.[11a, 12a]
Scheme 3
Scheme 3
Mn(hmds)2‐catalyzed hydroboration of nitriles, esters, amides, and pyridines. 1H‐NMR yields vs. internal hexamethylbenzene. [a] 10 mol % Li(hmds) instead of [Mn]. [b] 50 °C, 20 h. For details, see the ESI.
Scheme 4
Scheme 4
Mn(hmds)2 catalyzed hydroboration of carbodiimides, cyclic and linear carbonates, depolymerization of polyesters and polycarbonates, and carbon dioxide. 1H‐NMR yields vs. internal hexamethylbenzene. [a] 10 mol % Li(hmds) instead of [Mn], [b] 80 °C, 20 h, [c] 80 °C, 72 h in [D8]THF. Details are given in the ESI.
Scheme 5
Scheme 5
Key experiments and postulated mechanism (NR2=N(SiMe3)2).
See this image and copyright information in PMC

References

    1. None
    1. The Handbook of Homogeneous Hydrogenation (Eds.: de Vries J. G., Elsevier C. J.), Wiley-VCH, Weinheim, 2007;
    1. Nishimura S., Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis, Wiley, New York, 2001;
    1. Catalysis without Precious Metals (Ed.: Bullock R. M.), Wiley-VCH, Weinheim, 2010;
    1. Non-Noble Metal Catalysis: Molecular Approaches and Reactions (Ed.: Klein Gebbink R. J. M., Moret M.-E.), Wiley-VCH, Weinheim, 2019;

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