Diethoxymethyl protected pyrroles: Synthesis and regioselective transformations

Treatment of the acceptor-substituted pyrroles la-k with neat triethyl orth oformate gives access to the diethoxymethyl (DEM) protected derivatives 2a- k in high yield. Convenient and mild cleavage was achieved by subsequent tr eatment of the DEMpyrroles 2a-k with trifuoroacetic acid in acetonitrile an d aqueous NaOH at room temperature, DEM protection proved suitable for a va riety of regioselective transformations involving directed orthometalation and iodine-magnesium exchange processes, Furthermore, electrophilic halogen ations and Pd-catalyzed coupling reactions were also carried out.