Gold-Catalyzed Oxidative Cyclization Of Enynamides:A Stereoselective Approach To Tetracyclic Spiroindolines

Because of the supra reactivity towards the activation of C-C triple bond,the reactions triggered by cationic gold catalyst have received considerable attentions in the past decades.Diazo compounds are valuable building blocks.They can release molecule nitrogen in presence of a proper transition-metal catalyst to generate metal carbene intermediates which could further participate in a number of classic transformations.However,their synthetic potential is limited by toxic and explosive nature.Alkynes are readily available.The way to generate a-carbonyl carbene intermediates via gold-catalyzed oxidation of alkynes is a research subject of significant interest to the synthetic community since the safer character and sometimes even better reaction behaviors of the corresponding gold carbene intermediates.Tetracyclic spiroindolines are core structural motifs of a large number of natural products with interesting biological and phamceutical activities.As part of our continuing research interests in N-heterocyclic compound synthesis based on gold-catalyzed reaction ynamides,in this thesis,we have firstly designed and synthesized a variety of conjugated enyamides from simple starting materials,such as tryptamines,aldehydes and et.al.With these enyamides in hand,we then developed gold-catalyzed oxidative annulations using pyridine N-oxide as oxidant,giving tetracyclic spiroindolines in high yields and excellent diastcreo sclectivities.The salient features of current transformation arc mild reaction conditions,high yield,broad substrate scope,complete control on the stereoselectivity.Lastly,the products were characterized by NMR spectroscopy,high resolution mass spectrometry,infrared analysis and X-ray crystal analysis.