HOMOLYTIC SUBSTITUTION-REACTIONS OF ELECTRON-RICH PENTATOMIC HETEROAROMATICS BY ELECTROPHILIC CARBON-CENTERED RADICALS - SYNTHESIS OF ALPHA-HETEROARYLACETIC ACIDS

Efficient and selective homolytic substitutions (yields between 55 and 90%) of pyrrole, indole, and some pyrrole derivatives have been carried out using ambiphilic and electrophilic carbon centered radicals, generated in DMSO by Fe2+/H2O2 and alpha-cyano-, alpha-carbonyl-, and alpha,alpha'-dicarbonylalkyl iodides. The reaction is highly successful also with pyrroles substituted by electron-withdrawing groups, which has allowed an efficient synthesis of Tolmetin. A few extensions of this reaction to furan and thiophene are described.