Development of Transformations of Pyridotriazoles and Photoinduced Palladium Hydride-enabled Reactions

The thesis describes the development of denitrogenative transformations of pyridotriazoles and photoinduced palladium hydride-enabled reactions. A general and efficient method for arylation, X–H insertions, and cyclopropanation reactions of pyridotriazoles was developed. This protocol proceeded via pyridyl carbene intermediates, under mild, transition metal-free, and light-induced conditions. Furthermore, a Co-catalyzed transannulation reaction of pyridotriazoles with isothiocyanates and xanthate esters was developed. This method features the conversion of pyridotriazoles into two N-fused heterocycles, such as imino-thiazolopyridines and oxo- thiazolopyridine derivatives, via one-step Co(II)-catalyzed transannulation reaction proceeding though a radical mechanism. Next, three protocols enabled by visible light and palladium hydride were developed. A variety of substrates, such as diazo compounds, N-tosylhydrazones, strained molecules, acrylic acids, acrylic amides, and Baylis-Hillman adducts were found to produce hybrid palladium alkyl radical intermediates under photoinduced and palladium hydride-catalyzed conditions. These alkyl radical species subsequently participated in diverse transformations, including Heck reaction, hydroalkenylation and cascade annulation reactions.