Base-Catalyzed [3 + 2] Cycloaddition of N- Benzyl Ketimines to Arylacetylenes Followed by Oxidation: A One-Pot Access to Polyarylated 2 H -Pyrroles via Intermediate Pyrrolines.

N -Benzyl ketimines undergo [3 + 2] cycloaddition with arylacetylenes in the KOBu ^t /DMSO solution to 2,3,5-triarylpyrrolines, which are oxidized (chloranil, DDQ) in situ to 2,3,5-triaryl-2 H -pyrroles in 53-71% yields. The intermediate 1-pyrrolines can be isolated in 31-91% yields and separately oxidized to the corresponding 2 H -pyrroles.