Year: 2025
Type: article
Abstract: Carbanions are an important class of reactive species used as nucleophiles in C-C bond-forming reactions. Such reactive carbanions are generated by deprotonating relatively acidic C-H bonds using strong bases like sodium/potassium hydroxides or amides. Lochmann-Schlosser base, consisting of a mixture of alkyl lithium reagents and heavier alkali metal alkoxides, is widely used for the metalation of organic compounds via the deprotonation of weakly acidic C-H bond. The aggregation of alkoxides makes it challenging to understand the course of the reaction, demanding the consideration of molecular compounds as alternatives to sodium/potassium alkoxides. Here, we demonstrate the development of new organosodium reagents using molecular compounds as alternatives to oligomeric sodium/potassium alkoxides. Sodium tris(3,5-dimethylpyrazolyl)borate, along with mesityllithium in the presence of tris[2-(dimethylamino)ethyl]amine (Me6TREN) deprotonates benzylic C-H bonds. The resulting carbanions generated in the reaction mixtures are trapped as [(Me6TRENNa)2CH2C6H3(3,5-CH3)]+, [(Me6TRENNa)2CH2Ph]+ and [(Me6TRENNa)2CH2C6H4(3-CH3)]+, which represent distinct examples of structurally characterised sodium benzyl cations. Preliminary reactivity studies on [(Me6TRENNa)2CH2Ph]+ indicate that it functions as an efficient alkylating reagent. Further, [(Me6TRENNa)2CH2Ph]+ is used to investigate the catalytic reduction of olefins in the presence of PhSiH3. Computational investigations on the catalytic hydrosilylative reduction infer that the reaction is mediated by a hypercoordinate hydridosilyl anion stabilised across two sodium centres. These investigations lead to new prospects in organoalkali metal chemistry. Reactive carbanions are typically formed by deprotonating relatively acidic C–H bonds. Here, the authors demonstrate that combining sodium tris(pyrazolyl)borate with mesityllithium in the presence of a donor ligand generates a reactive organometallic mixture that deprotonates benzylic C–H bonds, enabling the isolation of cationic sodium benzyl species.
Source: Nature Communications
Authors: Suban Kundu, Kiran Raj, Alex P. Andrews, Thayalan Rajeshkumar, Laurent Maron, Ajay Venugopal
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $6,990
Award: G2232932938
OpenAlex ID: W4417498169