Studies On The Photoinduced Cyclization Reactions Of Halogenated Heterocyclic Compounds And Organic Azides

This dissertation deals with the studies on photoinduced cyclization reaction of halogenated heterocyclic compounds and organic azides. The content includes the following two parts.The first part is a brief review on the recent process made in the field of applying photochemistry to organic synthesis. This review summarizes the major achievements during the last twenty years with regarding to (1) the photoinduced dehalogenation reactions of aryl halides,(2) the photochemical pericyclic reactions, and (3) the photochemical reactions of organic azides.The second part describes the major research works during my graduate study, which is composed of the following three aspects:(1) An efficient synthesis of Paullone and kenpaullone derivatives has been achieved by employing the photoinduced dehalogenation cyclization of2-(2-chloro-1H-indol-3-yl)-N-arylacetamide s.(2) The photochemical reaction of3-(2-azidophenyI)-N-phenylacrylamides. This work demonstrates that under UV light irradiation,3-(2-azidophenyI)-N-phenyl acrylamides will first eliminate a nitrogen molecule to form nitrenes, and then to N-phenyl-indole-2-carboxamide derivatives through sequential intromolecular addition and hydrogen migration. Subsequent electrocyclic reaction and oxidative aromatization of the latter will lead to indolo[2,3-c] quinolin-6-ones. This work provides an efficient method for the synthesis of indolo[2,3-c] quinolin-6-ones.(3) The cyclization of iminyl radicals derived from azides. The part reveals that under visible light irradiation,2-azido-N-phenylacetamides will react with N-Bromo-succinimide (NBS) to afford the quinoxalin-2-ones or spiro[cyclohexene-1,2’-imidazoI]-4’-ones. The reaction involves iminyl radicals as the key intermediates. The substituents at the para position of phenyl ring have a large influence on the products:the electron-withdrawing groups favor the formation of quinoxalin-2-one, while their electron-donating counterparts renderspiro[cyclohexene-1,2’-imidazol]-4’-ones become the major products.