Remarkably Efficient Enantioselective Titanium(IV)−(R)-H8-BINOLate Catalyst for Arylations to Aldehydes by Triaryl(tetrahydrofuran)aluminum Reagents

Novel asymmetric triarylaluminum AlAr3(THF) additions to aldehydes catalyzed by 10 mol % of the titanium(IV) complex of (R)-H8-BINOL ligand are reported. The catalytic system is extremely efficient with reactions completing within 10 min. The system applies to the most diversified aldehydes to date, and more than 20 aldehydes were examined to afford diarylmethanols having an electron-donating or an electron-withdrawing group at the 2-, 3-, or 4-position on the aryl moiety, linear or branched 1-aryl aliphatic alcohols, aryl furyl methanols, 1-aryl allylic alcohols, and, especially, 1-aryl propargylic alcohols in excellent enantioselectivities of ≥90% ee, except for the case of 1-naphthyl addition to benzaldehyde. Noteworthily, diarylmethanols in both R- and S-configurations can be obtained.