Asymmetric Synthesis And Kinetic Resolution Of Polysubstituted Tetrahydrothiapyran Derivants

Enantioselective reactions catalyzed by small organic molecules(asymmetric organocatalysis)have emerged as one of the most elegant cutting-edge strategies of asymmetric synthesis over the last decade.Organocatalysis,by now,has definitively matured to a recognized third methodology,of potentially equal status to organometallic and enzymatic catalysis.Organocatalysts have several important advantages,since they are usually robust,inexpensive,readily available and non-toxic.Currently,chemists have successfully three-dimensional control many classic chemical reactions,such as aldol reaction,Mannich reaction,reaction Stetter,Henry reaction and Michael reaction by small organic molecules catalysts.we had synthesised a kind of polysubstituted tetrahydrothiopyran derivatives usingα,β-Unsaturated carbonyls and sodium sulfide.All the compounds have been confirmed by 1H NMR,13C NMR,HR-MS.It was found that:1)Solvent has a great influence in the reaction.Experiments show that using CH3CN:H2O=1:1 mixed solvent can get the highest yield;2)The reaction will be worse if substituent groups of the α,β-unsaturated carbonyls are larger.Common chiral catalysts were tried.The reactions were catalyzed by the chiral catalysts and the ee of the products were determined by HPLC.Asymmetric synthesis compound polysubstituted tetrahydrothiopyran.Derivative 3a.ee values up to 10.1%.We had synthesised compound 4a using compound 3a and acetic anhydride.Lewis acids such as zinc chloride,ferric chloridecan,stannic chloride,boron trifluoride diethyl etherate play a very significant catalytic effect on the reaction.Kinetic resolution of 3 a via enantioselective acylation:ee values up to 20%.