A Chiral Primary Amine Thiourea Catalyst for the Highly Enantioselective Direct Conjugate Addition of α,α-Disubstituted Aldehydes to Nitroalkenes

Simple cyclohexanediamine-derived primary amine thiourea catalyzed highly enantioselective conjugate addition of nitroalkanes to enones

A highly enantioselective conjugate addition of nitroalkanes to enones has been developed. The process is efficiently catalyzed by a simple chiral cyclohexanediamine-derived primary amine thiourea with a broad substrate scope.

Theoretical study of the catalysis of cyanohydrin formation by the cyclic dipeptide catalyst cyclo[(S)-His-(S)-Phe]

Dipeptide cyclo[(S)-His-(S)-Phe] 1, first applied by Inoue et al. in 1981, catalyzes the hydrocyanation of aromatic aldehydes very efficiently. Enantioselective autoinduction has also been reported for the process. We have employed QM (density functional theory and MP2), molecular mechanics (MM), and molecular dynamics (MD) methods to (i) derive a mechanistic picture for catalysis and (ii) reveal the origin of stereochemistry and autoinduction. A dimer is proposed to be the catalytic species, in which one imidazole group is essential for the delivery of the nucleophile and the second imidazole group acts as an acid, accompanied with pi-interaction for most favorable substrate binding. Hydrogen-bonding via hydroxy groups is crucial for catalysis also. MD studies indicate stability of the dimer only in non-polar media, which is consistent with the need of the experimental (heterogeneous) reaction conditions to achieve high enantioselectivities. DFT and MP2 results suggest the incorporation of the product cyanohydrin via extended edge-to-face pi-interaction over three aromatic units. Transition states derived from this model are in good agreement with experimental findings and enantioselectivities.

Highly enantioselective synthesis of gamma-nitro heteroaromatic ketones in a doubly stereocontrolled manner catalyzed by bifunctional thiourea catalysts based on dehydroabietic amine: a doubly stereocontrolled approach to pyrrolidine carboxylic acids

A new class of dehydroabietic amine-substituted primary amine-thiourea bifunctional catalysts were designed and synthesized. The doubly stereocontrolled organocatalytic conjugate addition of a variety of heterocycles-bearing ketones to nitroalkenes was investigated for the first time, affording (S)- or (R)-gamma-nitro heteroaromatic ketones with excellent enantioselectivities (up to ee >99%). Furthermore, the nearly optically pure gamma-nitro heteroaromatic ketones can be readily transformed into chiral pyrrolidine carboxylic acids.

Asymmetric aminocatalysis--gold rush in organic chemistry

Catalysis with chiral secondary amines (asymmetric aminocatalysis) has become a well-established and powerful synthetic tool for the chemo- and enantioselective functionalization of carbonyl compounds. In the last eight years alone, this field has grown at such an extraordinary pace that it is now recognized as an independent area of synthetic chemistry, where the goal is the preparation of any chiral molecule in an efficient, rapid, and stereoselective manner. This has been made possible by the impressive level of scientific competition and high quality research generated in this area. This Review describes this "Asymmetric Aminocatalysis Gold Rush" and charts the milestones in its development. As in all areas of science, progress depends on human effort.

Enantioselective organocatalytic conjugate addition of alpha-aminoketone to nitroolefins

The enantioselective organocatalytic conjugate addition of alpha-aminoketone to nitroolefins is reported.

Organocatalytic enantioselective Michael addition of 2,4-pentandione to nitroalkenes promoted by bifunctional thioureas with central and axial chiral elements

Two novel bifunctional amine-thiourea organocatalysts 1 and 2, which both bear central and axial chiral elements, have been developed to promote enantioselective Michael reaction between 1,3-dicarbonyl compounds and nitro olefins. The catalyst 2 afforded the desired products with good levels of enantioselectivity (up to 96% ee), showing clearly that two chiral elements of 2 are matched, and enhance the stereochemical control.