Direct Mannich and Nitro-Mannich Reactions with Non-Activated Imines: AgOTf-Catalyzed Addition of Pronucleophiles to ortho-Alkynylaryl Aldimines Leading to 1,2-Dihydroisoquinolines



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A variety of 1,2-dihydroisoquinoline derivatives 3 have been prepared in good to high yields by the AgOTf-catalyzed reaction of ortho-alkynylaryl aldimines 1 with various pronucleophiles 2 (see scheme). Treatment of 1 with a stoichiometric amount of AgOTf followed by protonation with TfOH produced 4, which suggests the formation of an isoquinolinium intermediate in the present direct addition reaction. Tf=trifluoromethanesulfonyl.