A Highly Active System for the Metal-Free Aerobic Photocyanation of Tertiary Amines with Visible Light: Application to the Synthesis of Tetraponerines and Crispine A

A highly efficient metal‐free catalytic system for the aerobic photocyanation of tertiary amines with visible light is reported. The use of air as terminal oxidant offers an improved safety profile compared with pure oxygen, the used compact fluorescent lamp (CFL) light sources are highly economical, and no halogenated solvents are required. This system not only proves to be effective for a wide variety of trialkylamines, pharmaceuticals, and alkaloids but remarkably also allows the lowest catalyst loading (0.00001 mol % or 0.1 ppm) ever reported for an organic dye. Bruylants reactions and C‐alkylation/decyanations were performed on the obtained α‐aminonitriles to demonstrate the postfunctionalization of complex molecules. The catalytic system is furthermore applied in the short and effective syntheses of the alkaloids (±)‐crispine A and the tetraponerines T7 and T8. Turn on the light: A simple and highly efficient photocyanation of tertiary amines with rose bengal, TMSCN, air, and visible light is presented. The broad scope and the synthetic potential of this method is demonstrated by the α‐cyanation of various alkaloids as well as by the total synthesis of crispine A and both enantiomers of the tetraponerines T7 and T8. The catalytic system shows activity down to 0.1 ppm catalyst loading.