Abstract
Arynes are highly reactive intermediates which possess numerous applications in organic synthesis. Arynes have been used in several transition metal-catalyzed reactions. Recently, efforts have been devoted to transition metal free reactions, which include the initial addition of nucleophiles to arynes and subsequent trapping with electrophiles. In this thesis, I reported a new method for the synthesis of (-phenanthrenyl)vinylsilanes from benzynes and allenylsilanes. Compounds containing phenanthrene moiety possess luminescence and fluorescence properties. Attachment of a silyl group directly to allenes allowed their reactions with substituted benzynes at 0 °C to produce (-phenanthrenyl)vinylsilanes exclusively in 66–92% yields through a [2 + 2 + 2] pathway. Without a silyl group in allenes, the reaction proceeded by entirely different pathways to give a mixture. These results indicate the existence of an unprecedented silicon-induced arene formation, of which mechanism and generality are discussed. To continue the study of transition metal free reactions involving arynes, I utilized these reactive intermediates arynes to develop a new aryne-induced reaction. I developed a new method for the synthesis of imidazolidines, a class of compounds with biological activities of value. By use of the 1,3-dipolar cycloaddition strategy, a Schiff base bearing an ester or a cyano group at the carbon atom was arylated with an aryne that were generated from (trimethylsilyl)aryl triflates and cesium fluoride. Then an intramolecular proton transfer took place from the position to the anionic aryne ring to give an azomethine ylide. This ylide reacted with a second equivalent of the same Schiff base in situ at 25 °C through a [3 + 2] fashion to produce the desired imidazolidines in 70–85%. This “one-flask” method proceeded with very high stereoselectivity that all of three substituents attached to the carbon atoms in the imidazolidine ring held in cis configuration. This is the first aryne-induced cyclization reported in the synthesis of five-membered heterocycles.