Assembly of 2-substituted tetrahydroquinolines from ortho-methylbenzenesulfamides and dienes, using a C(sp3)-H activation/ annulation sequence

Abstract

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.