Assembly of 2-Substituted Tetrahydroquinolines from ortho-Methylbenzenesulfamides and Dienes, Using a C(sp3)–H Activation/Annulation Sequence

1,2,3,4-Tetrahydroquinolines (THQs) are essential structural cores in many natural products and pharmaceutical drugs. Especially relevant are those presenting substitutions at position 2, yet practical methods for their one-step assembly from acyclic precursors are very scarce. Herein, we present a straightforward approach to assembling these skeletons from ortho-methylanilines using a palladium-catalyzed C(sp³)-H activation/formal cycloaddition sequence. Key for the success of the approach is the use of dienes as partners, since they lead to stable π-allyl palladium intermediates that prevent β-hydride elimination processes and allow installation of versatile alkenyl handles at position 2. Moreover, installing a perfluorobenzenesulfonyl substituent at the amine not only facilitates the C-H activation but also allows for an easy recovery of the free amine.