Unlocking azole chemical space via modular and regioselective N-alkylation.

Azoles are important synthetic targets due to their diverse applications in areas ranging from human health to food security. Accordingly, access to N-functionalized azoles is an essential goal in modern synthetic chemistry. Surprisingly, however, the relied-upon azole N-alkylation strategies fundamentally limit the structural diversity of these important compounds that can be synthesized and studied. Here we introduce an approach to prepare a broad array of important but difficult-to-access N-alkyl azole compounds. We accomplish this through the introduction of a base-catalysed hydroazolation of readily accessible alkenylthianthrenium electrophiles. This strategy circumvents the classical challenge of azole alkylation regiocontrol through an unusual reversible C-N-bond-forming step that exploits the thermodynamic differences between azole N-alkylation isomers. This reaction furnishes a class of versatile azolothianthrenium building blocks that provides a general platform to investigate diverse N-alkyl azole molecules. More broadly, the distinctive approach outlined through this project is poised to impact the design and development of diverse regioselective alkylation reactions.