Hydroboration of Nitriles, Esters, and Carbonates Catalyzed by Simple Earth‐Abundant Metal Triflate Salts

Abstract

During the past decade earth-abundant metals have become increasingly important in homogeneous catalysis. One of the reactions in which earth-abundant metals have found important applications is the hydroboration of unsaturated CÀ C and CÀ X bonds (X = O or N). Within these set of transformations, the hydroboration of challenging substrates such as nitriles, carbonates and esters still remain difficult and often relies on elaborate ligand designs and highly reactive catalysts (e. g., metal alkyls/hydrides). Here we report an effective methodology for the hydroboration of challenging C�N and C=O bonds that is simple and applicable to a wide set of substrates. The methodology is based on using a manganese(II) triflate salt that, in combination with commercially available potassium tert-butoxide and pinacolborane, catalyzes the hydroboration of nitriles, carbonates, and esters at room temperature and with near quantitative yields in less than three hours. Additional studies demonstrated that other earth-abundant metal triflate salts can facilitate this reaction as well, which is further discussed in this report.

Germanium Hydride Catalyzed Selective Hydroboration and Cyanosilylation of Ketones

“…Recently Fontaine, [21a] Ma, [21b] and Rueping's [21c] research groups demonstrated carbonate hydroboration using main group metal‐based compounds [21] . In 2021, Ruiter and coworkers reported the transition metal‐catalyzed hydroboration of carbonates [22] …”

Selective Nickel‐Catalyzed Hydrodeacetoxylation of Aryl Acetates

“…In both cases, the starting material remained stable with only a very small percentage of 4-propylguaiacol Our results indicate the formation of small amounts of byproduct 1 a under optimal conditions on 3 a are therefore likely the result of a Ni-catalyzed carbonyl hydroboration side reaction involving C=O rather than direct CÀ OAc bond cleavage, in accordance with recently reported transition metal-catalyzed hydroboration reactions of aryl acetates into alcohols. [27] The sterical nature of a t-Bu rationalizes why in esters the acetates are more prone to ArOH formation.…”

Organoaluminum hydrides catalyzed hydroboration of carbonates, esters, carboxylic acids, and carbon dioxide

“…Nevertheless, there are a few reports on the hydroboration of carbonates (Scheme 1). 29,[31][32][33][34] Thus, it is crucial to develop hydroboration reactions of Al-catalyzed carbonates under mild conditions.…”