Synthesis of -alkoxycarbonyl Pyrroles from -Substituted Carbamates: A Synthetically Enabling Pyrrole Protection Strategy.

The condensation of readily available -substituted carbamates with 2,5-dimethoxytetrahydrofuran gives -alkoxycarbonyl pyrroles in a single step and in good yield. By this method, several common amine protecting groups can be introduced on the pyrrole nitrogen. With the exception of -Boc, -alkoxycarbonyl groups have seen only minimal use for protection of the pyrrole nitrogen to date. Here, we show that -alkoxycarbonyl protection can endow pyrrole with distinct reactivity in comparison with -sulfonyl protection, for example, in a pyrrole acylation protocol employing carboxylic acids with a sulfonic acid anhydride activator.