Research Of Stereodivergent Transfer Hydrogenation Of Alkynes Under Cobalt,Nickel Catalyst Using Water As Hydrogen Source

Alkene structures are widely found in many bioactive natural products,such as resveratrol and its derivatives.The semi-reduction-hydrogenation reaction of alkynes is an effective method to construct bioactive alkene structure with single configuration,thus playing a very important role in organic reactions.Transfer hydrogenation is a hydrogenation reduction reaction using other hydrogen sources other than hydrogen.In recent years,our group has made a series of achievements in the study of asymmetric transfer hydrogenation,realizing the asymmetric transfer hydrogenation of borneene by alcohol,amine and water,and the asymmetric transfer hydrogenation of imine by alcohol as hydrogen source.Water as the greenest hydrogen source has become the focus of our follow-up research.This paper mainly introduces the research on the stereoselective semi-reduction transfer hydrogenation of alkynes with water as the hydrogen source under the catalysis of cheap transition metal cobalt or nickel.1.Under the cobalt-catalysis,we realized stereoselectivity semi-reduction hydrogenation of alkynes,the selectivity of alkene products can be siwtched by solvent and ligand with cobalt iodide as catalyst,water as a hydrogen source,zinc powder as the reductant,no ligand add and methanol as solvent and under the condition of given priority to with Z-alkenes,selectivity up to 95%,as ligands in dppe and acetonitrile as the solvent and under the condition of the E-alkenes is given priority to,selective as high as 97%;Experimental study on mechanism shows that under Z-conditions,water and methanol each provide one hydrogen,while under E-conditions,water is the only hydrogen source,and the reaction process has undergone hydrocarbon activation without isomerization.By expanding the substrates,the method shows a wide range of substrates,and is applied to the synthesis of resveratrol,showing a better application value.2.On the basis of previous studies,the stereoselective semi-reductive transfer hydrogenation of alkynes regulated by nickel salt anion was realized by using nickel salt as catalyst,and an interesting stereoselective regulation method was reported.Using the same strategy as the cobalt catalytic system,the interesting results were obtained.Using tetrahydrofuran as the solvent,under the NiX₂/Zn/H₂O catalytic system,obtained cisi-alkene by using Ni（OTf）₂,but NiI₂ obtained trans-alkene,the method showing good reactivity and stereosselectivity.Through the mechanism study,it is concluded that there is no isomerization process in the E-condition,and water is the only hydrogen source in the two conditions,which provides a green economy and efficient synthesis path for the relevant deuterium drugs.In conclusion,the transfer hydrogenation of alkynes with water as the source of hydrogen has been studied systematically in this paper,and the stereoselective selectivity of alkenes products was realized by ligands,solvents and metal precursors.