Copper‐Catalyzed Quadruple Borylation of Terminal Alkynes to Access sp3‐Tetra‐Organometallic Reagents

Copper‐catalyzed regioselective quadruple borylation of terminal alkynes has been developed employing a copper catalyst generated from CuI and dcpe (1,2‐bis(dicyclohexylphosphino)ethane). A wide range of terminal alkynes undergo this multi‐borylation reaction to afford the corresponding 1,1,2,2‐tetraborylalkanes in high yields. Mechanistic studies reveal that this quadruple borylation reaction proceeds through copper‐catalyzed sequential double 1,2‐diborylation of alkynes and 1,2‐diborylalkene intermediates. This protocol represents the most straightforward and atom‐economic approach to prepare sp3‐tetra‐organometallic reagents from readily accessible alkynes with commercially available copper catalysts. A chemoselective copper‐catalyzed quadruple borylation of terminal alkynes is developed to prepare synthetically versatile 1,1,2,2‐tetraborylalkanes with a catalyst generated from CuI and dcpe (1,2‐bis(dicyclohexylphosphino)ethane). Mechanistic studies reveal that this quadruple borylation reaction proceeds through sequential 1,2‐diborylation of alkynes and 1,2‐diborylalkene intermediates.