The Dual Role of Ruthenium and Alkali Base Catalysts in Enabling a Conceptually New Shortcut to N-unsubstituted Pyrroles Through Unmasked α-amino Aldehydes

A virtually salt-free and straightforward bimolecular assembly giving N-unsubstituted pyrroles through fully unmasked α-amino aldehydes, which was enabled by the dual effects of a catalytic ruthenium complex and an alkali metal base, is reported. Either solvent-free or acceptorless dehydrogenation facilitates high atom, step, and pot economy, which are otherwise difficult to achieve in multistep operations involving protection/deprotection.