Solvent‐Induced Reversal of Enantioselectivity in the Synthesis of Succinimides by the Addition of Aldehydes to Maleimides Catalysed by Carbamate‐Monoprotected 1,2‐Diamines

Abstract

A simple change in the polarity of the solvent allows both enantiomers of substituted succinimides to be obtained in the enantioselective conjugate addition reaction of aldehydes, mainly α,α‐disubstituted, to maleimides catalysed by chiral carbamate‐monoprotected trans‐cyclohexane‐1,2‐diamines. Using a single enantiomer of the organocatalyst, both enantiomers of the resulting Michael adducts are obtained in high yields by simply changing the reaction solvent from aqueous DMF (up to 84 % ee) to chloroform (up to 86 % ee). Theoretical calculations are used to explain this uncommon reversal of the enantioselectivity; two transition state orientations of different polarities are differently favoured in polar or nonpolar solvents.

Organocatalytic Asymmetric α-Chlorination of 1,3-Dicarbonyl Compounds Catalyzed by 2-Aminobenzimidazole Derivatives

“…This assumption was based on the fact that the reaction using catalyst 1 with NCS and 2,3,4,5,6,6-hexachlorocyclohexa-2,4-dienone as chlorine source rendered the corresponding product 5a with opposite configurations. The same stereodivergent [38][39][40][41][42] behavior was observed with catalyst 2.…”

“…the corresponding product 5a with opposite configurations. The same stereodivergent [38][39][40][41][42] behavior was observed with catalyst 2. Finally, and based on previous studies from our group on which chiral 2-aminobenzimidazolederived organocatalysts were employed in different reactions, tentative mechanisms can be proposed for methods A and B (Figures 2 and 3).…”

Solvent‐Dependent Enantiodivergent Friedel‐Crafts Reaction of Arylsulfonyl Indoles with 1‐Naphthols

“…Most related researchers have utilized covalent chiral secondary amines as the catalysts. [8] However, to the our knowledge, only two studies involving solvent-controlled enantiodivergent reactions by using noncovalent tertiary amine organocatalysts have been conducted. [3,9,10] Sohtome and Nagasawa reported a solvent-dependent enantiodivergent Mannich reaction of N-Boc imines with malonates by using a conformationally flexible guanidine/bisthiourea organocatalyst.…”

Asymmetric Michael Addition Organocatalyzed by α,β-Dipeptides under Solvent-Free Reaction Conditions

“…In this context, the Michael addition reaction is a particularly powerful method for C–C bond formation. Nevertheless, the enantioselective Michael addition reaction between enolizable aldehydes and maleimides [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ] or nitroolefins [ 28 , 29 , 30 , 48 , 49 , 50 , 51 , 52 , 53 ] has rarely been studied in relation to the reaction with cyclohexanone ( Scheme 1 ).…”