Synthesis of Highly Substituted Alkenes from Terminal Alkynes.

Alkenes make up an important class of compounds prevalent in biologically active molecules and synthetic intermediates. Their significance has driven the development of robust synthetic methods that allow the efficient and selective production of mono- and disubstituted alkenes. However, the selective synthesis of more highly substituted alkenes from readily accessible starting materials remains a significant synthetic challenge. Here, we present a novel approach for synthesizing tri- and tetrasubstituted alkenes through the catalytic coupling of terminal alkynes with alkylboranes and organohalides. The unique reaction mechanism ties the relative positioning of substituents in the alkene products to specific coupling partners that deliver them, enabling the efficient and precise generation of multiple isomers of tri- and tetrasubstituted alkenes from readily available precursors. We also demonstrate the coupling of alkylboranes with terminal alkynes in the presence of a proton source, which unexpectedly provides complementary stereoselectivity in the synthesis of trisubstituted alkenes to further broaden access to various isomers of highly substituted alkenes.