The sulphonation of indole and some of its simple alkyl derivatives

Abstract

The sulphonation of indole, 1-methyl-, 2-methyl-, and 1,2-dimethylindole by pyridinium-1-sulphonate in refluxing pyridine occurs smoothly at C3; analogous sulphonation of 3-methyl- and 1,3-dimethylindole occurs at C2; 2,3-dimethylindole does not react under these conditions. © 1973.