Chemistry of aminophenols. Part 2: A general and efficient synthesis of indoles possessing a nitrogen substituent at the C4, C5, C6, and C7 positions

A general and efficient synthesis of indoles possessing a nitrogen substituent at the C4, C5, C6, and C7 positions has been developed. Starting from commercially available nitro 2-aminophenols, 5-, 6-, and 7-arenesulfamoylindoles were synthesized via a base-promoted ring closure of 2-alkynylanilides, reduction of the nitro group, and sulfonylation. C4 nitrogen substituted indoles were synthesized from 2-chloro-1,3-dinitrobenzene via cyclization of 2-alkynyl-1,3-diaminobenzene as the key step.