Gold-Catalyzed "Back-to-Front" Synthesis of 4-Silyloxyindoles

A series of pyrrol-yn-glycol derivatives were easily prepared from simple pyrroles through a three-step sequence involving hydroxyalkylation-alkynylation-O-silylation. Their reaction with IPrAuNTf2 triggers a C2-pyrrole attack onto the activated alkyne and subsequent highly selective 1,2-migration of the oxyalkyl group in the intermediate spirocycle. This approach enables the efficient synthesis of a wide selection of regioselectively functionalized 4-hydroxyindoles, which represent important yet challenging indole scaffolds, in high yields.

Synthesis of 7-hydroxy-6,7-dihydro-indole and 6′,7′-dihydro-3,7′-biindole derivatives from domino reactions of arylglyoxals or methyl ketones with enamines

A series of interesting 7-hydroxy-2-aryl-6,7-dihydro-indol-4(5H)-ones 3 was successfully synthesized in moderate to good yields by the domino reactions of different arylglyoxals 1 with enamines 2 under catalyst-free conditions.

Synthesis of biologically important, fluorescence active 5-hydroxy benzo[g]indoles through four-component domino condensations and their fluorescence “Turn-off” sensing of Fe(iii) ions

The efficiently synthesized fluorescence active 5-hydroxy benzo[g]indoles show excellent fluorescence "Turn-off" sensing of Fe³⁺ ions.