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