Highly enantioselective Michael addition of aldehydes to nitroolefins catalyzed by primary amine thiourea organocatalysts

Regioselective and diastereodivergent organocatalytic asymmetric vinylogous Michael addition

Regioselective and diastereodivergent γ-position asymmetric vinylogous Michael addition (AVMA) of cyclohex-2-enones to nitroalkenes and γ′-AVMA between cyclohex-3-enones and nitroalkenes.

Novel chiral proline-based organocatalysts with amide and thiourea–amine units for highly efficient asymmetric aldol reaction in saturated brine without additives

A series of novel proline-based organocatalysts with amide and thiourea-amine units (7a–7f) were developed and evaluated in the asymmetric aldol reaction of 4-nitrobenzaldehyde with cyclohexanone. The organocatalyst (7c or 7d, 5 mol%) exhibited efficient catalytic activity to afford aldol products in high diastereoselectivity (up to >99:1), enantioselectivity (up to >99%), and yield (up to >96%) at 0 °C in saturated brine without adding an acid. Aldol products of benzaldehyde derivatives almost universally provide high diastereoselectivity and enantioselectivity.

Mechanistic Insight into Fast and Highly Efficient Organocatalytic Activity of a Tripodal Dimeric Hexaurea Capsular Assembly in Michael Addition Reactions

A tris(2-aminoethyl)-amine-based dimeric capsular assembly of pentafluorophenyl urea (C1) has been employed as a catalyst in a wide range of Michael addition reactions. This capsular catalyst assembly dramatically accelerates the Michael addition reaction of β-nitrostyrenes (2a-2d) with various Michael donors such as ketoesters (3a, 3e), 1,3-diketones (3b), diesters (3C), and cyanoesters (3d) at room temperature to yield the corresponding nitroalkanes in significantly high yields within a very short reaction time. Significant improvement in solubility and use of conventional organic solvents in reaction along with a drastic decrease in reaction time (high value of the rate constant of the reaction) has been achieved through C1 as compared to the previously reported homologous tripodal monomeric urea catalyst (L1). The addition of enolate to β-nitrostyrenes to generate an anionic intermediate seemed to be highly stabilized by the six urea units of capsular assembly. Control experiments and in situ kinetic studies are performed for this addition reaction and based on the results, a plausible mechanism has been proposed for the formation of Michael adduct inside the capsular cavity.

Asymmetric Conjugate Addition of α,α-Disubstituted Aldehydes to Nitroalkenes Organocatalyzed by Chiral Monosalicylamides from trans-Cyclohexane-1,2-Diamines

Primary amine-salicylamides derived from chiral trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to arylated and heteroarylated nitroalkenes. The reaction is performed in the presence of 4-dimethylaminopyridine as an additive in dichloromethane as a solvent at room temperature. The corresponding enantioenriched γ-nitroaldehydes are obtained with enantioselectivities up to 95%. Theoretical calculations are used to justify the reasons of the stereoinduction.

Bifunctional primary amine-thioureas in asymmetric organocatalysis

Research disclosed since the demonstration of the first examples of primary amine-thiourea organocatalysis in 2006 has shown that primary amine-based thioureas can successfully catalyze a diverse variety of highly enantioselective transformations providing a wide range of versatile organic compounds. Recent remarkable progress with these chiral catalysts is summarized in this review.