Diethoxymethyl Protected Pyrroles: Synthesis and Regioselective Transformations

Abstract

Treatment of the acceptor-substituted pyrroles 1a-k with neat triethyl orthoformate gives access to the diethoxymethyl (DEM) protected derivatives 2a-k in high yield. Convenient and mild cleavage was achieved by subsequent treatment of the DEM-pyrroles 2a-k with trifluoroacetic acid in acetonitrile and aqueous NaOH at room temperature. DEM protection proved suitable for a variety of regioselective transformations involving directed ortho-metalation and iodine-magnesium exchange processes. Furthermore, electrophilic halogenations and Pd-catalyzed coupling reactions were also carried out.

Key words

protecting groups - pyrroles - metalations - Suzuki-coupling - Sonogashira reaction - halogen-metal exchange

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