Chemodivergent 1,3-Dipolar Cycloadditions of ,-Cyclic Azomethine Imines with γ-Sulfonamido-α,β-Unsaturated Ketones to Synthesize Tricyclic Dinitrogen-Fused Heterocycles.

1,3-Dipolar cycloadditions of ,-cyclic azomethine imines with γ-NHTs-α,β-unsaturated ketones were developed to synthesize tricyclic dinitrogen-fused heterocycles. Highly functionalized tricyclic tetrahydroisoquinolines were readily obtained in good to high yields in the [3 + 2]-cycloaddition reaction of -Bz-protected ,-cyclic azomethine imines with γ-NHTs-α,β-unsaturated ketones under mild reaction conditions. Moreover, DABCO-catalyzed cycloaddition of -Ts-protected ,-cyclic azomethine imines with γ-NHTs-α,β-unsaturated ketones followed by cleavage of the tosyl group is a convenient route to synthesize tetrahydropyrazolo [5,1-]isoquinolines in good yields with excellent diastereoselectivities.