Organocatalyst Efficiency in the α‐Aminoxylation and α‐Hydrazination of Carbonyl Derivatives in Aqueous Media or in a Ball‐Mill

• Published in: European journal of organic chemistry Vol. 2017; no. 8; pp. 1191 - 1195
• Main Authors: Veverkova, Eva, Modrocka, Viktoria, Sebesta, Radovan
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 24.02.2017
• Subjects: Aldehydes; Aminoxylation; Asymmetric synthesis; Ball mill; Chemistry; Chemistry, Organic; Hydrazination; Organocatalysis; Physical Sciences; Science & Technology; Ball mill; SOLVENT-FREE CONDITIONS; Aldehydes; Organocatalysis; SHORT ENANTIOSELECTIVE SYNTHESIS; AMINOOXYLATION; Aminoxylation; Hydrazination; ASYMMETRIC ALDOL REACTION; AMINATION; Asymmetric synthesis; AMINO ALDEHYDES; MICHAEL ADDITIONS; (S)-PROLINE-CONTAINING DIPEPTIDES; PROLINE; WATER
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201601357

Pyrrolidine‐derived organocatalysts have been tested in two types of α‐heterofunctionalization reactions in aqueous media or under solvent‐free ball‐milling conditions. The best results in terms of both activity and enantioselectivity were obtained with O‐silylated 4‐hydroxyproline derivatives in the α‐aminoxylation reaction between n‐butyraldehyde and nitrosobenzene (83 % yield in water, 86 % yield by ball milling and ee > 99 %). A very good yield (82 %) and excellent optical purity (ee > 99 %) were also achieved in the α‐hydrazination reaction of 3‐phenylpropanal with dibenzyl azodicarboxylate by the ball‐milling technique. The application of aqueous media and solvent‐free conditions have been assessed in the asymmetric organocatalytic α‐aminoxylation and hydrazination of aldehydes. Both sets of conditions considerably speed up these reactions, while maintaining high enantioselectivity.