A highly diastereoselective one-pot Ugi/radical spirocyclization/aza-Michael addition sequence

We hereby report a highly diastereoselective synthesis of chalcogenated azaspirotricycles via a one-pot Ugi/spirocyclization/aza-Michael addition sequence. The reaction proceeds via a key visible light mediated spirocyclization step under mild, metal-free and energy efficient conditions. A variety of complex sulfenylated and selenylated azaspirotricycles were obtained in good yields. The reaction was found to be scalable and preliminary mechanistic studies indicated that the spirocyclization step proceeds via radical intermediates. Highly diastereoselective sequence consisting of eosin-Y catalyzed radical spirocyclization of post-Ugi adducts with aryl thiols or aryl diselenides followed by aza-Michael addition provided access to complex azaspirotricycles in an efficient manner.