Stereospecific alkyl-alkyl cross-coupling of boronic esters

Cross-coupling of aryl boronic esters forms a cornerstone of how chemists make molecules. More recently, enantiomerically enriched boronic esters have shown great promise in modular synthesis as versatile building blocks for the rapid construction of diverse molecules. A significant challenge in this area is to use boronic esters for the catalytic construction of C(sp³)-C(sp³) bonds, especially those in which the reaction site is a stereogenic carbon centre. Addressing this challenge would not only expand the utility of boronic esters in the modular synthesis of organic frameworks, but also prove more broadly beneficial in the synthesis of natural products and bioactive molecules¹. In this connection, we have developed a stereospecific C(sp³)-C(sp³) coupling reaction catalysed by a copper acetylide complex. This reaction operates with four-coordinate boron-'ate' complexes while remaining inert to simple functional groups, including boronic esters, and thereby enables efficient strategies for modular synthesis of complex molecules. Applications to the synthesis of (-)-spongidepsin and the carbon skeleton of fluvirucinine A₁ are described.