Asymmetric Reductive Aldol-Type Reaction with Carbonyl Compounds Using Dialkyl Tartrate as a Chiral Ligand

Abstract

An asymmetric reductive aldol-type reaction of α,β-unsaturated esters with carbonyl compounds using Rh catalyst and Et 2 Zn was investigated. A chiral zinc complex from α,β-unsaturated ester was easily generated as the key intermediate from Et 2 Zn and Wilkinson's catalyst with diisopropyl L-( )-tartrate to give a variety of enantioenriched β-hydroxy esters. The reaction was also applied to the intramolecular reductive aldol cyclization.

Rh-Catalyzed reductive Mannich-type reaction and its application towards the synthesis of (±)-ezetimibe

“…In some of our previous publications [ 22 – 23 36 ], we proposed a reaction mechanism as shown in Fig. 1 .…”

Reductive Carbon–Carbon Bond Forming Reactions with Carbonyls Mediated by Rh–H Complexes

“…The Rh-catalyzed aldol reaction could be applied to the enantioselective reaction. [13] We conducted a series of reactions to determine the most effective chiral ligand, and the use of (+)-diisopropyl L-tartrate as the ligand was found to be optimal. The scope and limitations of the asymmetric system are summarized in Table 3.…”

Zinc Acetate Catalyzed Enantioselective Reductive Aldol Reaction of Ketones

“…While an example of the chiral Rh complex in presence of zinc salt has been presented by Ando in 2014, the role of Et 2 Zn was limited only to generation of rhodium hydride complex. [11] Previously, we elaborated expedient protocols for the asymmetric hydrosilylation of prochiral ketones and imines by using readily available chiral Zn(OAc) 2 complexes in situ forming zinc hydride as an active intermediate. [12] This prompted us to predict that the chiral zinc hydride complex may be a cheaper and easy formed equivalent of Cu-based catalysts.…”