Syntheses of chiral hybrid O,N-donor ligands for the investigation of lanthanide complex reactivities in direct aldol condensations

Catalytic enantioselective intramolecular Tishchenko reaction of meso-dialdehyde: synthesis of (S)-cedarmycins

The first successful example of a catalytic enantioselective intramolecular Tishchenko reaction of a meso-dialdehyde in the presence of a chiral iridium complex is described. Chiral lactones were obtained in good yields with up to 91% ee. The obtained enantioenriched lactones were utilized for the first synthesis of (S)-cedarmycins A and B.

Directed ortho,ortho'-dimetalation of hydrobenzoin: Rapid access to hydrobenzoin derivatives useful for asymmetric synthesis

A variety of ortho,ortho'-disubstituted hydrobenzoin derivatives are readily accessible through a directed ortho,ortho'-dimetalation strategy in which the alcohol functions in hydrobenzoin are deprotonated by n-BuLi and the resulting lithium benzyl alkoxides serve as directed metalation groups. The optimization and scope of this reaction are discussed, and the utility of this process is demonstrated in the one-pot preparation of a number of chiral diols as well as a short synthesis of the chiral ligand Vivol.

Direct enantioselective aldol-Tishchenko reaction catalyzed by chiral lithium diphenylbinaphtholate

Chiral lithium diphenylbinaphtholate is an effective catalyst for the enantioselective aldol-Tishchenko reaction, affording 1,3-diol derivatives with three contiguous chiral centers and high stereoselectivities. Successive aldol-aldol-Tishchenko reactions gave a triol derivative with five consecutive chiral centers. The present reaction was applicable to highly enantioselective Evans-Tishchenko reduction.

Chiral Ytterbium Complex-Catalyzed Direct Asymmetric Aldol-Tishchenko Reaction: Synthesis ofanti-1,3-Diols

The asymmetric aldol-Tishchenko reaction of aromatic aldehydes with aliphatic and aromatic ketones has been developed as an efficient strategy for the synthesis of anti-1,3-diols in good yield with high diastereocontrol and good levels of enantioselectivity. This domino-type reaction is catalyzed by a chiral ytterbium complex that promotes both the aldol reaction through enolization of the carbonyl compound and the Evans-Tishchenko reduction of the aldol intermediate. The stereochemistry of the resulting diols is also investigated and finally proved by using CD techniques.

Enantioselective direct aldol-Tishchenko reaction: access to chiral stereopentads

[reaction: see text] The aldol-Tishchenko reaction of aromatic aldehydes in the presence of titanium(IV) tertbutoxide and amino alcohols is described. When used with cinchona alkaloids, stereopentads were isolated for the first time with a high degree of diastereo- and enantioselectivity.

Direct asymmetric aldol-Tishchenko reaction of aliphatic ketones catalyzed by syn-aminoalcohol–Yb(iii) complexes

The asymmetric direct aldol condensation of aldehydes with ethyl- and propylketones is catalyzed by syn-alpha-aminoalcohol-Yb(OTf)3 complexes, yielding the anti-1,3-diol monoesters with high diastereocontrol and good enantioselectivity. Three adjacent stereogenic centers are created in a simultaneous aldol condensation and Evans-Tishchenko reduction in an acyclic system.