An unconventional photochemical tetrahydroisoquinoline synthesis from sulfonylimines and alkenes

Tetrahydroisoquinolines (THIQ) are prevalent scaffolds found in natural products and pharmaceutical agents. Therefore, new methods for the synthesis of this motif, especially with unique stereochemistry or substitution patterns, are highly desirable. Herein, a new disconnection is demonstrated that combines sulfonylimines and alkenes. The convergent process operates by photoinduced energy transfer. High selectivities for the formation of the anti-isomer were observed. In addition, through the use of highly substituted alkenes, the synthesis of quaternary carbon containing tetrahydroisoquinolines can be achieved. Finally, mechanistic studies are included, revealing that the high selectivity observed is due to subtle variation of the highest occupied molecular orbital (HOMO) energies.