Enantioselective addition of ArTi(OⁱPr)₃ to aldehydes catalyzed by a titanium complex of an N-sulfonylated amino alcohol

Abstract

Asymmetric additions of aryltris(2‐propoxo)titanium to aldehydes are catalyzed by a chiral N‐sulfonated amino alcohol and afford optically active diarylmethanols with good to excellent enantioselectivities.

Recent developments in enantioselective titanium-catalyzed transformations

“…Ever since, other highly efficient chiral ligands have been applied to promote the asymmetric titanium-catalyzed aryl transfer to aldehydes at 0 °C. For example, these authors investigated chiral N-sulfonylated amino alcohol ligands in the addition of ArTi(Oi-Pr)3 to aldehydes 2, in 2015 [26]. As shown in Scheme 10, the process performed at 0 °C in the presence of 10 mol% of optimal ligand 13 in THF as solvent afforded the corresponding chiral alcohols 6 in good to quantitative yields (55-98%) and low to excellent enantioselectivities (3-95% ee).…”

“…Re-face attack Scheme 10. Arylation of aromatic/aliphatic aldehydes with ArTi(Oi-Pr)3 in the presence of chiral N-sulfonylated 1,2-amino alcohol ligand 13 [26].…”

Recent Advances in the Synthesis of Enantiomerically Enriched Diaryl, Aryl Heteroaryl, and Diheteroaryl Alcohols through Addition of Organometallic Reagents to Carbonyl Compounds

“…In subsequent work in 2015, Gau, Zhou, and co-workers reported the application of N-sulfonylated amino alcohol 25 in the enantioselective addition of ArTi(OiPr) 3 to aldehydes. 75 Selected examples are shown in Scheme 28. A wide range of aldehydes were used and, in all cases the yields of the diarylmethanols were high.…”

Selective Synthesis of Ketones and Chiral Allylic Alcohols from the Addition of Arylboronic Acids to α,β-Unsaturated Aldehydes Mediated by a Transition Metal/Monophosphorus Ligand System

“…In addition, self-hydrogen transferring isomerization, selective epoxide opening/alkylation, allylation of β-chloro ketones, α-arylation of enolates, chemoselective reduction of α,β-unsaturated ketones, and acylative Suzuki coupling have also been used. On the other hand, the preparation of chiral allylic alcohols typically involves enantioselective hydroboration of α,β-unsaturated ketones and 1,2-additions to α,β-unsaturated aldehydes of, e.g., arylboronic acids and organometallic compounds of zinc, lithium, titanium, magnesium, or aluminum (Scheme b); other methods are detailed elsewhere …”