Indirect Anti-Markovnikov Hydrofunctionalization of Terminal Alkenes via an Alkenyl Thianthrenium Intermediate.

The anti-Markovnikov hydrofunctionalization of terminal, unactivated olefins is an evergreen synthetic challenge in organic chemistry. Several direct and indirect anti-Markovnikov methods have been developed, ranging from the classical hydroboration/oxidation protocol to state-of-the-art photoredox catalytic, transition-metal-complex-catalyzed, and enzymatic procedures. Despite the ever-expanding suite of synthetic capabilities, these methods still have limited generality in their substrate scope, especially with nucleophiles. Herein, we show that terminal, unactivated olefins can be transformed into anti-Markovnikov products via an alkenyl thianthrenium intermediate that undergoes sequential hydride and nucleophile addition. The strategic advantage of this method lies in the ability to utilize a diverse array of oxidatively sensitive nucleophiles as reaction partners. This is accomplished through a mechanistically distinct, two-stage dication pool anti-Markovnikov approach, where separate oxidative olefin activation by thianthrenation is followed by the selective generation of a reactive alkyl thianthrenium salt.