Catalytic Addition of Indole-2-Carboxylic Acid to 1-Hexyne

Abstract

<jats:p>The synthesis of two novel enol esters, namely hex-1-en-2-yl indole-2-carboxylate and hex-1-en-2-yl 1-(hex-1-en-2-yl)-indole-2-carboxylate, is presented. Both compounds were generated by addition of indole-2-carboxylic acid to 1-hexyne employing [RuCl2(η6-p-cymene)(PPh3)] and [AuCl(PPh3)]/AgPF6, respectively, as catalysts.</jats:p>

Gold-Catalyzed Addition of Carboxylic Acids to Alkynes and Allenes: Valuable Tools for Organic Synthesis

“…As observed with [AuCl(PPh3)], mixtures of regioisomers were in most cases obtained when non-symmetrically substituted alkynes were used as substrates. Very recently, the catalytic addition of indole-2-carboxylic acid to hex-1-yne was explored with different ruthenium and gold catalysts [95]. As shown in Scheme 32, by employing catalytic amounts of [AuCl(PPh3)]/AgPF6 in toluene at 100 °C, the reaction led to the enol ester 74, which resulted from the addition of both the acid and NH groups of the indole derivative to hex-1-yne molecules.…”