Chemoselective Benzylation of Aldehydes Using Lewis Base Activated Boronate Nucleophiles

Abstract

A benzylation of aldehydes using primary and secondary benzylboronic acid pinacol esters is reported. Activation of the boronic ester with s-butyllithium rendered it nucleophilic toward aldehydes. The activated nucleophile chemoselectively transfers the benzyl group over the s-butyl group, providing excellent yields of the benzylated products. 11B NMR experiments were performed to study the mechnism of this transformation.

Site‐Selective 1,2‐Dicarbofunctionalization of Vinyl Boronates through Dual Catalysis

“…As initially anticipated, a canonical oxidation with NaBO 3 cleanly delivered 11 in good yields . Likewise, a series of C−C bond‐forming reactions could easily be conducted via C−B bond cleavage in 4 r , including Pd‐catalyzed Suzuki–Miyaura reactions ( 9 ), or the incorporation of heterocycles ( 8 ), vinyl halides ( 10 ), or ketone backbones ( 6 , 7 ) in one‐pot procedures. Taken together, the data shown in Schemes – serves as a testament to the prospective impact of our 1,2‐difunctionalization method.…”

Transition Metal‐Free sp3−sp3 Carbon‐Carbon Coupling between Benzylboronic Esters and Alkyl Bromides

“…This approach is attractive in that it does not require the use of a transition metal eliminating the often‐toxic metal byproducts. We have demonstrated our dialkylboronate nucleophile reacts with aldehydes, aldimines and ketones [9–11] …”

“…We have demonstrated our dialkylboronate nucleophile reacts with aldehydes, aldimines and ketones. [9][10][11] There was an interest in identifying additional electrophiles compatible with our dialkylboronate intermediate in order to make sp 3 À sp 3 carbon-carbon bonds. Alkyl halides were chosen as electrophiles to pursue this type of bond formation.…”

Benzylation of Imines with Activated Boronate Nucleophiles

“…Aggarwal has previously employed aryllithium reagents to activate alkylboronic esters and their subsequent reactions in numerous enantiospecific transformations . Previously, we have demonstrated benzylboronic acid pinacol ester (BnBpin) can be activated by an alkyllithium reagent, rendering it nucleophilic toward aldehydes …”