Photoorganocatalytic Aerobic Oxidative Amine Dehydrogenation/Super Acid-Mediated Pictet-Spengler Cyclization:Synthesis of cis-1,3-Diaryl Tetrahydroisoquinolines

Aerobic oxidative dehydrogenation reactions of benzylamines to imines were studied and the efficiencies of various ground- and excited state quinone organocatalysts were compared. Long wave-absorbing anthraquinones readily catalyze the aerobic photodehydrogenation of primary and secondary benzylamines to benzylidenebenzylamines with high rate and selectivity, and the reaction mechanism was studied by laser flash photolysis. Further, branched α-benzyl dibenzyl-amines undergo a regioselective photocatalytic dehydrogenation to branched aldimines, which can efficiently be converted into cis-1,3-diaryl tetrahydro-isoquinolines through diastereoselective super acid-mediated Pictet-Spengler cyclizations. (Figure presented.).