We hereby describe an instance of diastereoselective trifluoromethanesulfonic
acid catalyzed 1,3-dipolar cycloaddition of a trifluoromethylated
azomethine imine with α,β-ethenyl ketones. Using
two different reaction conditions, reaction of trifluoroacetaldehyde
phenylhydrazone and chalcone derivatives gave polysubstituted pyrazolidines
and pyrazolines derivatives with efficiency and high diastereoselectivity.
pyrazolines - hydrazone - copper triflate - trifluoromethanesulfonic acid - cycloaddition