Direct Catalytic Asymmetric Aldol Reaction:  Synthesis of Either syn- or anti-α,β-Dihydroxy Ketones

Characterization of Dimeric and Tetrameric μ‐Hydroxide Ytterbium(III) Binaphtholate Complexes

“…[1-6] These bifunctional catalysts are exceptional in their ability to catalyze a broad range of asymmetric transformations, such as the Henry reaction, [1,7] conjugate additions, [4,5,[7][8][9][10] aldol condensations, [6,11] cyanoethoxycarbonylation of aldehydes, [12] and hydrophosphonylation of aldehydes and cyclic imines, [13,14] to name a few. Despite the widespread successful application of these heterobimetallic catalysts in asymmetric synthesis, their reaction mechanisms are not well understood, because their multifunctional nature complicates mechanistic studies.…”

The Direct Catalytic Asymmetric Aldol Reaction

“…The LLB·KOH complex was able to catalyze an enantio-and diastereoselective direct aldol reaction with 2-hydroxyacetophenone, which provided the anti-α,β-dihydroxy ketones (Scheme 4). [7] It is also noteworthy that chiral aldehydes containing an acidic α-hydrogen atom can produce the corresponding aldol products with negligible racemization (0Ϫ4%). This reaction was found to be catalyst-controlled.…”

Linked-BINOL: An Approach towards Practical Asymmetric Multifunctional Catalysis

“…We also reported an enantio-and diastereoselective direct aldol reaction with 2-hydroxyacetophenone (44a), which provided anti-a,b-dihydroxy ketones using a LaLi 3 tris(binaphthoxide) ¥ KOH (LLB ¥ KOH) complex ( Figure 12 and Scheme 5). [50] We hypothesized that a unique property inherent in the linked-BINOL 10 would also provide an effective direct aldol reaction.…”

“…[50,51] Although the structure of 45 has not yet been clarified, we propose the ate complex depicted as [Zn(OAr) 4 ] 2À Zn 2 ( Figure 12) based on the property of this semi-crown ether type ligand and the X-ray structure of the Ga-Li-linked-BINOL complex ([Ga(OAr) 4 ] À Li ). Attempts to obtain X-ray grade crystals of Zn-Zn-linked-BINOL are currently underway in our laboratory.…”