Regioselective and Stereodivergent C–H Functionalization of Internal Alkenes

Herein, we introduce a new strategy for the regioselective and stereodivergent C–H functionalization of internal alkenes. We discovered that the regioselectivity of internal alkene thianthrenation is exceptionally electronically sensitive and can be controlled by native allylic and homoallylic functional groups. We also found that both alkenyl thianthrenium stereoisomers can be selectively accessed by using different workup conditions. While thianthrenation is typically stereoretentive, the addition of Cs2CO3 in the workup induces isomerization through reversible conjugate addition. We show that both stereoisomers of the alkenyl linchpins can be readily engaged in stereoretentive cross coupling reactions. This selective thianthrenation-coupling sequence introduces a generalizable platform for stereodefined trisubstituted alkene synthesis.