Research On 2-(phenylethynyl)pyridines Mediated Pd-catalyzed Seletive Heck Reaction And Synthesis Of Nature Perfume

The dissertation consists of two parts:1)2-(phenylethynyl)pyridines ligands mediate Pd-catalyzed seletive oxidative Heck reaction;2)Synthesis of natural perfume 2-isobutyl-3-methoxypyrazine.Chapter 1:The Heck-Mizoroki coupling reaction is one of the most powerful transformations for the construction of C-C bonds and has the potential for broad synthetic application.Unfortunately,a key problem remains that how to control the position where aryl groups intert into olefins.The ability to use unfunctional alkenens as substrates rather than vinyl halides represents a significant advantage over other cross-coupling methods for the synthesis of substituted alkenes.For electronically biased olefins such as styrene,vinyl ethers and acrylates,high regioselectivity can be achieved easily.Typically,electron-deficient alkenes such as acrylates and styrenes favor couping at the terminal position to give linear products,while electron-rich alkenes favor couping at the internal position to give the branched products.(Scheme 1).However,the development of regioselective Heck reactions using electronically unbiased alkenes,especially for aliphatic olefins,as substrates in a catalytic manners is formidable challenge.Over the past decades,various bidentate nitrogen ligands in complex with palladium have been successfully applied to the Heck coupling reactions.On the other hand,several groups have demonstrated that a PdⅡ center could coordinate with the N and the C ≡ C Bond simultaneously.Bearing these knowledge in mind,several pyridine-type ligands containing C ≡ C bonds were designed and employed in selective oxidative Heck reaction.To our surprise,L3 shows good yield,ln/br selectivity and moderate regioisomeric ratio.Chapter 2:Natural perfume 2-isobutyl-3-methoxypyrazine is synthesized from natural Leucine.Leucine undergoes esterification,ammonolysis,condensation and substitution reaction to pruduce 2-isobutyl-3-methoxypyrazine.Cheap raw materials,simple operation and mild conditions make the synthetic route useful in industrialized synthesis.