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

Abstract

AbstractA 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.