Iridium-Catalyzed anti-Diastereo- and Enantioselective Carbonyl (α-Trifluoromethyl)allylation from the Alcohol or Aldehyde Oxidation Level

Asymmetric Synthesis of Adjacent Tri- and Tetrasubstituted Carbon Stereocenters: Organocatalytic Aldol Reaction of an Hydantoin Surrogate with Azaarene 2-Carbaldehydes

A bifunctional amine/squaramide catalyst promoted direct aldol addition of an hydantoin surrogate to pyridine 2-carbaldehyde N-oxides to afford adducts bearing two vicinal tertiary/quaternary carbons in high diastereo- and enantioselectivity (d.r. up to >20:1; ee up to 98 %) is reported. Acid hydrolysis of adducts followed by reduction of the N-oxide group yields enantiopure carbinol-tethered quaternary hydantoin-azaarene conjugates with densely functionalized skeletons. DFT studies of the potential energy surface (B3LYP/6-31+G(d)+CPCM (dichloromethane)) of the reaction correlate the activity of different catalysts and support an intramolecular hydrogen-bond-assisted activation of the squaramide moiety in the transition state of the catalytic reaction.

Enantioselective Iridium-Catalyzed Phthalide Formation through Internal Redox Allylation of Phthalaldehydes

An inside job: Enantioselective phthalide synthesis was achieved through internal redox allylation of o-phthalaldehydes. Oxidative esterification is balanced by reductive carbonyl addition to achieve an overall redox-neutral process. This method enabled formal syntheses of ent-spirolaxine methyl ether and CJ-12,954.

Diastereo- and Enantioselective Iridium Catalyzed Carbonyl (α-Cyclopropyl)allylation via Transfer Hydrogenation

The first examples of diastereo- and enantioselective carbonyl α-(cyclopropyl)allylation are reported. Under the conditions of iridium catalyzed transfer hydrogenation using the chiral precatalyst (R)-Ir-I modified by SEGPHOS, carbonyl α-(cyclopropyl)allylation may be achieved with equal facility from alcohol or aldehyde oxidation levels. This methodology provides a conduit to hitherto inaccessible inaccessible enantiomerically enriched cyclopropane-containing architectures.

Catalytic enantioselective C-H functionalization of alcohols by redox-triggered carbonyl addition: borrowing hydrogen, returning carbon

The use of alcohols and unsaturated reactants for the redox-triggered generation of nucleophile-electrophile pairs represents a broad, new approach to carbonyl addition chemistry. Discrete redox manipulations that are often required for the generation of carbonyl electrophiles and premetalated carbon-centered nucleophiles are thus avoided. Based on this concept, a broad, new family of enantioselective C-C coupling reactions that are catalyzed by iridium or ruthenium complexes have been developed, which are summarized in this Minireview.