Date : 2011. 3. 10, 5:00 PM Place : Int"l conf. room, Bldg 25-1 -Abastract-    The advantage of using gold complexes for catalysis derives from their unusual ability to activate alkyne, allene, and alkene toward the nucleophilic attack. When they activate these -bonds, the resulting intermediate species resemble a classical cationic intermediate, which is highly reactive and often follow a cascade cyclization pathway for a rapid assembly of useful intermediates. By introducing various cation-trapping groups, we disclosed various tandem annulations using Au(I)- and Au(III)-complexes.1-3 Also along this line, I will present an addition of tertiary amines onto alkynes forming quaternary ammonium salts. While this addition mode provides a modular route to N-quat salts for potential applications in phase-transfer catalysis, studies on the reaction mechanism indicates the importance of mass-transfer of counter-anion for catalyst turnover and an interesting and unusual acidity at alpha vinyl-C-H bond. For additions on alkenes, I will present an atom-economical one-step synthesis of α,β -unsaturated-δ-lactones via a formal [4+2]-cycloaddition of styrene and propiolic acid.    Second aspects that our group is focusing on, is redox-economical reactions mediated by N-O bond substrates. 4-6 Gold-catalyzed redox reactions of these substrates generate a variety of highly reactive intermediates, such as carbene, azomethine ylide, imine and enolate. For example, we have established a new synthetic equivalence between readily available alkynyl nitrones and 3-oxidopyridinium betains for [3+2] cycloaddition through the catalysis of Au(III)-complexes. Also, utilizing this redox cascade, I will present cascade assembly of pharmaceutically interesting heterocycles as well as 3-pyrrolidinones and nitrones. Through these examples, I hope to demonstrate that hydroxylamine derivatives that are cheap and operationally safe and can be appealing oxidant that shows a versatile reactivity through N-O bond cleavage.