Decatungstate‐Photocatalyzed Functionalization of α‐Imino Esters for the Preparation of Unnatural α‐Amino Acid Derivatives

• Published in: ChemCatChem 2023-05, Vol.15 (9), p.n/a
• Main Authors: Jorea, Alexandra, Raviola, Carlotta, Giustiniano, Mariateresa, Ravelli, Davide
• Format: Article
• Language: English
• Subjects: Aldehydes; Amino acids; decatungstate anion; Esters; Herbicides; Hydrogen atoms; photocatalysis; radical reaction; α-amino acids; α-imino esters
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202300042

A library of unnatural α‐amino acid derivatives has been prepared via the hydrofunctionalization of the C=N bond in a set of compounds belonging to the family of α‐imino esters. The devised methodology capitalizes on the use of tetrabutylammonium decatungstate as the photocatalyst to generate C‐centered radicals from aliphatic and aromatic aldehydes, cyclic and acyclic oxygenated compounds and even cycloalkanes, via a hydrogen atom transfer (HAT) step. The best performance was observed when α‐hydrazono esters were employed in the role of radical traps, which delivered the corresponding (protected) α‐hydrazino acids as products. The versatility of the protocol was further demonstrated by the possibility to functionalize the herbicide safener isoxadifen‐ethyl. The hydrofunctionalization of α‐imino ester derivatives with aldehydes, oxygenated compounds and cycloalkanes has been realized under decatungstate‐photocatalyzed conditions. The best performance was offered by α‐hydrazono derivatives containing a sulfonyl group, while the versatility of the protocol was further demonstrated by the smooth functionalization of the herbicide safener isoxadifen‐ethyl.