Transition Metals Involved Com-bined Catalysis And Their Appli-cation In Organic Synthesis

Combined catalytic strategy is a new synthetic method by using synergistic or relay catalytic functionalization of multiple catalysts in one reaction system, which can ef-fectively capture the unstable intermediates to achieve new reactions. In the field of modern synthetic chemistry, transition-metal catalysis is a very important and efficient synthetic method and has dominated the industrial catalytic reactions. The combination of transition-metal catalysis with enzyme catalysis, Lewis acid catalysis or organoca-talysis can break through the limitation of single catalyst system for the synthesis of complex molecules in one single step, from simple and easily available starting mate-rials. This paper discribes several application of transition-metals involved combined catalytic strategy in asymmetric catalysis and synthesis.We have developed a novel relay catalytic cascade intramolecular hydrosiloxylation of arylacetylene and asymmetric Mukaiyama aldol "one pot" reaction for the synthesis of chiral β-hydroxyl carbonyls, by using gold complex and chiral Br(?)nsted acid binary system. Moreover, the skeleton structures of phenylpropanoid and metasequirin B are able to be obtained from derivatizations of the reaction products in several steps.In order to achieve the total synthesis of metasequirin B, we have first developed a new organo-catalyzed asymmetric allylic alkylation of allyl alcohols and1,3-two car-bonyl compounds in the presence of chiral phosphoric acids. Then we accomplish the first catalytic asymmetric synthesis of hydroxylmetasequirin A and metasequirin B de-rivatives in several steps, and confirm their structures by single crystal results.By the combination of palladium(II) complex and (salen)CrCl, we have developed the first C-H activation based olefination reaction between terminal alkenes and a-diazo esters, providing a new approach for the synthesis of polyenes. Contrast experiments reveal that Lewis acids can effectively activate the diazo compounds, enhance their nucleophilic ability to facilitate the formation of transition-metal carbenoids.At last, we have developed a highly enantioselective α-allylation reaction of alde-hydes with terminal alkenes by combining asymmetric counteranion catalysis and pal-ladium catalyzed allylic C-H activation. A wide variety of a-methyl-branched aromatic aldehydes and terminal alkenes are able to undergo the C-H activation-based asymmet-ric allylic alkylation to afford good to excellent enantioselectivity. More importantly, this work actually demonstrates a general strategy for enantioselective functionalization of inactive C-H bonds and will provide an alternative platform for the creation of new enantioselective C-H/C-H coupling reactions.