Highly Enantioselective Aryl Addition Of ArLi To Aldehydes Catalyzed By The Complex Of （S）-H₈-BINOL-Ti

Enantioenrich diarylmethanols exhibit important biological and medical properties. Therefore, a lot of methods used to synthesize these kinds of compounds have been developed. For example, one of the most efficient and simple approaches to their preparation is the catalytic asymmetric arylzinc addition to aromatic aldehydes in the presence of a chiral ligand.Aryllithium reagents are one of the least expensive and commonly employed organometallic reagents. They are rarely used in the catalytic addition to aldehydes because of their high reactivity even much more than Grignard reagents. In this thesis, we report a highly asymmetric catalytic addition to aldehydes by using aryllithium reagents. Herein one-pot catalytic asymmetric syntheses of the enantioenrich diarylmethanols beginning from readily available aryl bromides are introduced. Thus, lithium-bormide exchange with commercially available aryl bromides and n-BuLi was followed by salt metathesis with AlCl3to generate Ar3Al. In the presence of enantioenriched (S)-H8-BINOL as chiral ligand, the ArTi(O’Pr)3coming from Ar3Al with Ti(O’Pr)4was added to aldehydes to afford essentially racemic diarylmethanols. At first, the low enantioselectives and yields were attributed to a LiCl-promoted background reaction. So we add the TMEDA to inhibit the background reaction. Under these conditions, enantioenriched diarylmethanols were obtained with up to99%yield and96%ee. One-pot reactions are easy and safe. The catalystic asymmtric reactions can complete after24hours at room temperature, and if we set the reactions at40℃after added the aldehyde, the catalystic asymmtric reactions will complete within about6hours and without loss of the enantioselectivities.