Highly Enantioselective Addition Of Linear Alkyl Alkynes To Aromatic Aldehydes

Objective:The chiral propargyl alcohol is an important intermediate for the synthesis of natural products,drugs and complex macromolecular compouds.The asymmetric addition of terminal alkynyls to aldehydes is an important way to obtain chiral propargy alcohols.Therefore,in this paper,the asymmetric addition of linear alkyl alkynes to aldehydes to prepared chiral propargyl alcohols was studied.Methods:In our study,we applied the system of BINOL-Et2Zn-Ti(O’Pr)4 to highly enantioselective reactions of linear alkyl alkynes to aromatic aldehydes.We also test the impact on the reaction yield a nd enantiomeric excess(ee)from the different solvent for the two st eps,different terminal acetylenes,different aldehydes as well as the amount of reactants and conditions.We use toluene and THF as s olvents for step 1 and step 2 under room temperature,with the sca le of n(alkyne)/n(Et2Zn)=1:1,n(alkyne)(4 mmol)/n(BINOL)(0.4 mmol)/n(Ti(O’Pr)4)(1.0 mmol)/n(aldehyde)(1.0 mmol)=20:2:5:5.Results:Comparing to other groups,the BINOL-Et2Zn-Ti(OiPr)4 system catalyses the asymmetric addition of linear alkynes to aldehydes and gains good yield of 68%to 92%and high ee of 74%to 95%under significant shortening the reaction time and without any other additives.