Synthesis of (Z)-1-Thio- and (Z)-2-Thio-1-alkenyl Boronates via Copper-Catalyzed Regiodivergent Hydroboration of Thioacetylenes: An Experimental and Theoretical Study

Abstract

A Cu-catalyzed divergent hydroboration of thioacetylenes has been achieved, providing (Z)-1-thio- or (Z)-2-thio-1-alkenyl boronates in moderate to high yields with excellent regio- and stereoselectivity, by using pinacolborane or bis(pinacolato)diboron as the hydroborating reagents, respectively. DFT calculations indicate that the sulfur atom plays a key role in determining the regioselectivity through polarizing the C-C triple bonds and participating in the HOMO orbitals. Moreover, the SR group can serve as a good leaving group, resulting in the concise synthesis of six regio- and stereoisomers of trisubstituted alkenes 5 via the iterative cross-coupling of C-B and C-S bonds. Clearly, it will be valuable for assembling stereochemically diverse trisubstituted olefins in organic synthesis.