A facile synthetic approach towards two distinct pyrrole-based heterocyclic scaffolds
has been developed by the interaction of 1H-pyrrole-2,3-diones fused at the [e]-side to a 1,4-benzoxazin-2-one or quinoxalin-2(1H)-one moiety with ketones. The described interaction proceeds either as an aldol reaction
or as a Michael addition/intramolecular cyclization depending on the reaction conditions.
The disclosed aldol reaction proceeds with good diastereoselectivity under catalyst-free
conditions when the reaction is carried out in aromatic hydrocarbons. Products of
the cascade Michael addition/intramolecular cyclization reaction are predominantly
formed under catalyst-free and solvent-free conditions. The proposed strategy provides
facile access to pharmaceutically interesting pyrrole-based polyheterocycles.
Key words
aldol reaction - fused-ring systems - Michael addition - nitrogen heterocycles - polycycles
