Catalytic Asymmetric Torgov Cyclization: A Concise Total Synthesis of (+)-Estrone

,An asymmetric Torgov cyclization, catalyzed by a novel, highly Bronsted acidic dinitro-substituted disulfonimide, is described. The reaction delivers the Torgov diene and various analogues with excellent yields and enantioselectivity. This method was applied in a very short synthesis of (+)-estrone.