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The N-alkylation of primary nitrophenylsulfonamides followed by removal of the nitrophenylsulfonamide moiety under nucleophilic conditions to provide secondary amines has become an established literature procedure. Application of this methodology with less reactive alkylating agents can give rise to side products resulting from a nitrogen to carbon transfer of the nitrophenyl ring. This side product predominates when tetrabutylammonium hydroxide is used in place of metal carbonate bases in the N-alkylation step.

The bifunctionality of amino acids can be exploited by utilizing them as quenchers in rapid solution phase parallel synthesis. The amino group was used to covalently trap the excess electrophiles, whereas the carboxylic acid moiety was used to solubilize the derivatized amino acid in water. As a prototype we used potassium sarcosinate as a quencher for excess electrophiles in the acylation or sulfonation of N-methyl-benzylamine. Various electrophilic reagents such as acid chlorides, isocyanates and sulfonyl chlorides were quenched successfully to give pure products in excellent yields.