Metalation of N-tert-butylthiophene-2-sulfonamide with n-butyllithium occura competitively at the 3-and 5-position of the thiophene ring. Equilibration of the initial mixture of Carbanions or metalation with lithium dihpropylamide allows selective formation of the N, 5dilithiothiopheneulfonamide 7. This dianion is useful for the preparation of a number of 5- substituted thiophene-2-sulfonamides.
