Palladium-catalyzed Synthesis Of Endiynes Base On Bromoalkynylation Of Alkynes

Construction of C(sp) C(sp~2) bond is an important method for the synthesis of various conjugated structures and biologically active compounds. Among different protocols for achieving this goal, coupling between substituted alkenes and terminal alkynes stands as the most employed method. Alkynes are one of the most important raw materials in organic synthesis, especially the development of the terminal alkynes have attracted the interest of the chemical researchers. Recently, several mild and convenient methods have been reported and thus have increased the attractiveness of haloalkynes in organic synthesis. This type of reaction has signicant advantages, the alkyne proceeds the coupling reaction with the halogen atom as the leaving group. Halogen atom could activate the triple bond and as the directing group, the triple bond occurs the electrophilic addition reaction. The halogen atom as the protective group replaces the terminal alkyne which proceeds the carbon hydrogen functionalization reactions.Our objectives are to develop catalytic system to selectively form C C and C X bonds to create useful molecules such as the alkenes wih sp~2 carbon halogen bond, from readily available terminal alkynes or haloalkynes. Our research on activation and functionalisation of alkynes has led to a series of new results which will be presented in the following two chapters.In Chapter 1, we have introduced the reaction features of haloalkynes, the effective synthesis methods and the progress on selective C C, C N, C O, C X bond formation from haloalkyns, and introduces the significane of this research subject.In Chapter 2, we have presented the first example of a palladium catalyzed highly regio and stereoselective haloalkynylation reaction to alkynes using simple haloalkynes, which are easily available from commercial vendors, to afford the haloalkenynes derivatives efficiently. The products could be functionalized through transition metal catalyzed reactions, such as Sonogashira coupling reactions. The reaction affords the corresponding endiynes from haloalkenynes first and then transforms to the products via Sonogashira Coupling reaction with terminal alkynes through palladium and copper iodide catalysis.