Transition-metal Gold Or Platinum Catalysis Cascade Reactions Of Allenes

Allenes are important units in many natural products. In addition, many natural compounds containing allenes show good biological activities and may have potential applications in the fields of synthesis chemitry. Thus, much attention has been focused on the development of new methodologies for using allenes high activity. Our group has demonstrated that the transition metal-catalyzed tandem reactions of allenes are effective in constructing many heterocyclic ring compounds and synthons. Based on these results, this dissertation consists of the following four parts.PartⅠNovel Platinum-Catalyzed Tandem Reaction:An Efficient Approach to Construct Naphtho[1,2-b]furanAn efficient approach to synthesize naphtho[1,2-b]furan has been developed via platinum-catalyzed tandem reaction. This new tandem catalysis comprises a cycloisomerization of allenyl ketones, followed by 6π-electrocyclization type reaction of carbene intermediate. The metal carbene intermediate was proved to be an excellent parameter in the 6π-electrocyclization type reaction.PartⅡSynthesis of Substituted 1,2-Dihydropyridines from Propargyl Vinyl Ethers And Allenic Vinyl Ethers by Gold-catalyzed Claisen Rearrangement and 6π-Aza-electrocyclization.An efficient synthetic methods were developed for the construction of substituted 1,2-dihydropyridines by gold-catalyzed tandem reactions. The key intermediates 2,4-Dienals are generated from propargyl vinyl ethers or allenic vinyl ethers with gold catalysts. These two reactions involve the process of gold-catalyzed [3,3]-sigmatropic rearrangement/isomerization/amine condensation/6π-aza-electrocyclization.PartⅢA Novel Platinum and Palladium Dual- Catalyzed One-pot Reaction:An Efficient Approach to Synthesis ofα-Allylated α,β-Unsaturated KetonesA novel method for synthesis of various substituteda-allylatedα,β-unsaturated ketones via a dual-metal catalytic one pot reaction has been developed. This new one pot catalysis comprises a platinum catalyzed [3,3]-sigmatropic rearrangement and a palladium-catalyzed allylic alkylation. This reaction provides access tpα-allylatedα,β-unsaturated ketones in moderate to good yield.PartⅣA Dual-metal Catalyzed One-pot Reaction:Access to Substituted 1,2-Diketones/ 2-Acyloxy EnonesA concise method for preparation of 1,2-diketones/2-acyloxy enones has been developed utilizing a novel dual-metal catalyzed one-pot reaction. Two different types of catalyst, PtCl2 and Pd(OAc)2, sequentially promote each catalytic cycle in one pot. It is proposed that the reaction proceeds via a platinum catalyzed double migrations and a palladium catalyzed intramolecular Tsuji-Trost reaction.