Intermolecular water attack to alkenylgold carbenes derived from 3-propargylindoles

An intermolecular hydroxylation of α,β-unsaturated gold carbene intermediates, generated from readily accessible 3-propargylindoles through a tandem 1,2-indole migration-hydroxylation sequence using water as an external nucleophile, has been developed. Under mild reaction conditions and employing gold(I) catalysts bearing bulky and electron-rich phosphine ligands, a significant range of hydroxy-functionalized indole derivatives was synthesized in high yields. Mechanistic studies support the selective addition of water to the β-position of the electrophilic α,β-unsaturated gold carbene intermediate, whereas competing attack at the carbene center or direct hydration of the activated alkyne was not observed.