Cyanoguanidine is an inexpensive commodity chemical and it is found to be a useful reagent for the direct Friedel-Crafts carboxamidation of arenes. The reaction works best in an excess of Bronsted superacid, an observation suggesting the involvement of a superelectrophilic intermediate. Theoretical calculations indicate that the most stable diprotonated species involves protonation at the guanidine and cyano nitrogen atoms.
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We gratefully acknowledge the support of the NIH- National Institute of General Medical Sciences ( GM085736-01A1 ).