Iridium-Catalyzed C-3 Allylation of Indoles with Allylic Alcohols Promoted by a Brønsted Acid

Abstract

A highly regioselective method has been developed for the allylation of indoles with an iridium catalyst. This regioselective procedure uses allylic alcohols directly as allylating agents in the presence of a catalytic amount of sulfuric acid. A wide range of indoles reacted smoothly with asymmetrical allylic alcohols to give the corresponding branched products in branched-to-linear ratios of up to 99:1 and yields as high as 92%. A series of inorganic and organic acids were tested in this approach, and it was shown that acids with pK _a values in acetonitrile of less than 15 are required in this iridium-catalyzed system.

Key words

iridium - allylations - indoles - regioselectivity - homogeneous catalysis

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