Decarboxylative Halogenation of Indolecarboxylic Acids Using Hypervalent Iodine(III) Reagent and Its Application to the Synthesis of Polybromoindoles

Abstract

Hypervalent iodine mediated decarboxylative halogenation of indoledicarboxylic acid derivatives was studied.The treatment of 1-methylindole-2,3-dicarboxylic acid with phenyliodine diacetate (PIDA) in the presence of lithium bromide gave 1-methyl-3,3-bromooxindole.However, the reaction of 1-(phenylsulfonyl)indole-2,3-dicarboxylic acid with PIDA in the presence of lithium bromide afforded 2,3-dibromo-1-(phenylsulfonyl)indole.In a similar manner, the 2,3-dichloro-and 2,3-diiodoindole derivatives could be obtained by the reaction of the indole-2,3-dicarboxylic acids with PIDA in the presence of lithium chloride and iodide.This method was optimized to the synthesis of polybromoindole alkaloids.