First Catalytic Asymmetric Aldol-Tishchenko Reaction-Insight into the Catalyst Structure and Reaction Mechanism

Abstract

Unmodified carbonyl compounds are converted in an enantioselective aldol‐Tishchenko reaction directly into the chiral adduct by using catalytic amounts of a chiral base prepared in situ [Eq. (1)]. The catalyst was developed through the combination of arrayed catalyst evaluation and informed ligand design. Ad=adamantyl.

Metal–Salen Schiff base complexes in catalysis: practical aspects

“…Morken describes another active yttrium complex, prepared by a different route in the enantioselective variant of a Tishchenko reaction. 54 The combination between yttrium and the chiral Salen 5 was found in a combinatorial approach, in which several other ligands and metals were examined. The complex prepared using Y 5 O(OiPr) 13 is seven-coordinated and bridged by two hydroxide ions to a second yttrium atom.…”

Synthesis, structure and reactivity of samarium complexes supported by Schiff-base ligands

“…Lanthanide complexes bearing N 2 O 2 tetradentate Schiff-base ligands are efficient catalysts for the asymmetric epoxidation of a,b-unsaturated ketones [8], ringopening polymerization of lactide and related cyclic esters [9][10][11]. Chiral yttrium-salen complexes are reported to be excellent catalysts for enantioselective acyl transfer reactions between enolesters and secondary alcohols [12], asymmetric Aldol-Tishchenko reactions [13] and the ring-opening of epoxides mediated by TMSCN and TMSN 3 [14]. Bis(salicyladiminato) scandium complexes can be used as efficient hydroamination of alkene catalysts [15].…”

Strategies to Bypass the Taxol Problem. Enantioselective Cascade Catalysis, a New Approach for the Efficient Construction of Molecular Complexity

“…42 Almost 60 years later, Morken and co- workers reported the first example of a catalytic asymmetric aldol-Tishchenko reaction using a yttrium-salen catalyst system. 43 More recently, Shibasaki and coworkers have developed a highly stereoselective aldol-Tishchenko procedure using the lanthanide-BINOL catalyst system, 44 previously effective in their seminal studies on the direct asymmetric aldol reaction. 45 Although the substrate scope was limited to electron-deficient aryl ethyl ketones and aryl/heteroaryl aldehydes, excellent levels of diastereoselectivity and enantioselectivity were observed for the isolated diols (of type 13, Equation 1).…”