Diversifying the superbase-catalyzed C=N bond ethynylation: triaryl-1-pyrrolines and triaryl-1H-pyrroles from N-benzyl aldimines and arylacetylenes

N-Benzyl aldimines react with arylacetylenes in the presence of Bu^tOK/DMSO superbase system to afford 2,3,5-triaryl-1-pyrrolines as two tautomers with 1,2- and 1,5-location of the double bond, both being the trans-diastereomers. This version of the C=N bond ethynylation differs from the previous one with N-benzyl ketimines. The oxidation of the pyrroline tautomeric mixtures without their isolation gives 2,3,5-triaryl-1H-pyrroles.