Base Mediated 1,2-Carboboration: Direct Access to Multisubstituted Alkenyl and Alkylboronates

We have developed a base-mediated 1,2-carboboration of commercially accessible alkynes for the construction of regio- and stereodefined alkenylboronates. This unprecedented reaction is enabled by sodium ethoxide (NaOEt) as a base and alkyl halide as an electrophile, with B₂pin₂ under mild reaction conditions. The protocol is simple, clean, and more economical compared to reported transition metal-catalyzed systems. The highlights of this methodology include readily available precursors, broad substrate scope and functional group compatibility, gram scale synthesis, and late-stage functionalization of alkenylboronates. The reaction is also applicable for the carboboration of alkenes. Experimental results and density functional theory (DFT) calculations provide insights into the mechanism.