Enolate trapping with various electrophiles is decidedly less common . In one study , the Nazarov cyclization is paired with a Michael reaction using an iridium catalyst to initiate nucleophilic conjugate addition of the enolate to β @-@ nitrostyrene . In this tandem reaction the iridium catalyst is required for both conversions : it acts as the Lewis acid in the Nazarov cyclization and in the next step the nitro group of nitrostyrene first coordinates to iridium in a ligand exchange with the carbonyl ester oxygen atom before the actual Michael addition takes place to the opposite face of the R @-@ group .