Photoinduced decarboxylative azidation of cyclic amino acids

Abstract

The direct decarboxylative azidation of cyclic α-amino acids has been achieved via visible light-mediated organo-photoredox catalysis.

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

“…Other organic dyes, including several acridinium salts, have been successfully applied in organophotocatalytic decarboxylation protocols. For example, rhodamine 6G (OD14, E(PC + */PC) ≈ 1.2 V) [42] was used for the photocatalytic decarboxylative azidation of cyclic amino acids and rose bengal (OD15) [43] for a decarboxylative amination of indoline-2carboxylic acids with azodicarboxylate esters.…”

Photocatalytic methods for amino acid modification

“…26). 50 Using a rhodamine-based photocatalyst, proline residues were decarboxylated to form the secondary alkyl radical, which was then trapped with an azide transfer reagent. The reaction proceeded in excellent yield when applied to N-Boc proline (87%), but the yields dropped when the procedure was attempted on dipeptides (54-68%).…”

Recent Advances in Photocatalytic Decarboxylative Coupling Reactions in Medicinal Chemistry

“…In 2019, Leonori and co-workers developed a photoinduced decarboxylative azidation of cyclic and tertiary amino acids. 58 Azides are widely used in drug discovery programmes as precursors to amines 59 and triazoles; 60 functionalities commonly found in bioactive compounds. 61 Reaction of a variety of carboxylic acids with arenesulfonyl azide 160, using either 5 mol% rhodamine 6G 161 or 9-mesityl-10-methylacridinium perchlorate as photocatalyst and CsOBz under irradiation with green LEDs led to the formation of a range of azides in moderate to good yields (Scheme 28).…”

“…76 In 2015, Nicewicz and co-workers described a mild organocatalytic photoredox system for the decarboxylative reduction of carboxylic acids (Scheme 38). 77 Acridinium 56,58 photooxidants were identified as suitable catalysts due to their high excited state oxidation potentials. Treatment of 220 with 5 mol% of photoredox catalyst Mes-Acr-Ph, 10 mol% (PhS) 2 , and 20 mol% i-Pr 2 NEt in TFE under 450 nm LEDs led to formation of decarboxylated 221 in 97% yield.…”