Diels–Alder trapping vs. amidoalkylation of cyclopentadiene with polychloroacetaldehyde sulfonylimines

The reaction of chloral or dichloro(phenyl)acetaldehyde N-arylsulfonylimines with cyclopentadiene, depending on the reaction conditions, affords either Diels–Alder adducts, 2-arylsulfonyl-2-azabicyclo[2.2.1]hept-5-enes, or unexpectedly new amidoalkylated derivatives of cyclopentadiene, N-[(cyclopentadienyl)(polychloromethyl)methyl]arenesulfonamides.