Sulfur-Based Protecting Groups for Pyrroles and the Facile Deprotection of 2-(2,4-Dinitrobenzene)sulfinyl and Sulfonyl Pyrroles

The effectiveness of simple sulfinyl and sulfonyl groups as electron-withdrawing protecting groups for pyrroles has been analyzed using 13C NMR spectroscopy and confirmed by consideration of X-ray crystal structures. Additionally, the 2,4-dinitrobenzenesulfinyl and sulfonyl groups are shown to be effective electron-withdrawing protecting groups for pyrroles, and they can be removed by treatment with benzene thiol or thiolate under mild and specific conditions.