Nitroalkenes as Latent 1,2-Biselectrophiles - A Multicatalytic Approach for the Synthesis of 1,4-Diketones and Their Application in a Four-Step One-Pot Reaction to Polysubstituted Pyrroles

An NHC-catalyzed nitro-Stetter/elimination/Stetter reaction sequence employs nitroalkenes as latent 1,2-dication synthons providing a novel access to highly useful symmetrical and unsymmetrical 2-aryl substituted 1,4-diketone building blocks from commercially available aldehyde precursors. For less activated (aliphatic) aldehydes, a cooperative catalytic strategy has been developed via the merger of NHC and H-bonding catalysis. To further showcase the versatility of our approach, a great variety of these unprecedented 1,4-diketones are used to efficiently synthesize polysubstituted pyrroles-including those with hetaryl substituents in good to excellent yields in a multicatalytic metal-free, four-step one-pot cascade reaction under mild, yet robust, conditions.