Multi-component Reactions Based On Trapping Of Active Ylides With Alkynals And α,β-Unsaturated Carbonyl Compounds

Multi-component reactions (MCRs) have attracted a great deal of attention because they provide rapid and convenient approaches to construct diverse and complex molecules from various simple starting materials. MCRs possess the advantages of high synthetic efficiency, atom economy, convergence and simplicity. Thus, the research and application of this field demonstrates profound academic significance.Recently, our group has reported a novel ammonium/oxonium ylide trapping transformation, in which an ammonium/oxonium ylide can be trapped by nucleophiles such as aldehydes, imines and Michael acceptors. However, the substrates in these new reactions are still limited. In this dissertation, we designed and implemented two types of ylide trapping multi-component reactions, one was based on using alkynals as substrate to trap oxonium ylide; the other was based on using 4-oxo-enoates as Michael acceptor to trap oxonium ylide.In chapter 1, relevant literatures were briefly reviewed, including diazo compound, carbine, yilde chemistry, and ylide participated multi-component reactions, etc. In addition, the background and strategies of this dissertation were also introduced.In chapter 2, non-aryl aldehydes were involved in this ylide trapping reaction for the first time. Our research shows that alkynals can efficiently capture the active oxonium ylide intermediate which is in situ generated from an alcohol or water and a metal carbenoid. The reactions afford (3-alkynyl-a, (3-dihydroxy acid esters in good yield with high diastereoselectivity (up to 96:4). The advantage of introducing an alkynyl functionality was demonstrated by converting this versatile group to other useful molecules. Dihydroxy enelactones can be efficiently made by simple transformation of the three-component coupling products In chapter 3, for the first time, we achieved trapping oxonium ylide by 4-oxo-enoates. Our research found that 4-oxo-enoates, as a Michael acceptor, can trap the oxonium ylide via a 1,4-addition with excellent diastereoselectivity (>99/1). The three-component reaction provides an efficient and distereoselective access to y-keto esters, which can be converted to y-butyrolactones through simple procedure.In this dissertation, we also studied other substrates, including nitroalkene and oxindole in ylide trapping reaction. Some intra-molecule cyclization by trapping oxonium ylide were also investigated.