Asymmetric Synthesis of 1,1,1-Triarylethanes by Chiral Imidodiphosphoric Acid Catalyzed Nucleophilic Addition of Pyrrole and Indoles to 3-Vinylindoles.

Chiral imidodiphosphoric acids were employed as efficient catalysts in the enantioselective addition reaction of pyrrole and indoles to 3-vinylindoles. A series of optically active 1,1,1-triarylethmanes bearing quaternary stereocenters were synthesized in excellent yields (up to 99% yield) and enantioselectivities (up to 98% ee). Gram-scale reactions of 1i and 2a as well as 1o and 5a demonstrated the synthetic utility of this methodology. Control experiments showed that the formation of a double H-bond between the catalyst and substrates is necessary for an excellent outcome.

Enantioselective Domino Reaction of 3-Vinylindole and p-Quinone Methides Enabled by Chiral Imidodiphosphoric Acids: Asymmetric Synthesis of Multisubstituted 3-Indolyl Cyclopenta[b]indoles.

The development of a stereoselective method for the rapid assembly of structurally complex molecules remains fascinating and challenging in synthetic organic chemistry. Here, we report an enantioselective domino reaction between 3-vinylindole and p-quinone methide for the preparation of 3-indolyl cyclopenta[b]indoles containing multiple chiral centers. Chiral imidodiphosphoric acids enable this cascade asymmetric process, delivering a series of products with excellent yields (≤99%), enantioselectivities (≤99%), and diastereoselectivities (≤20:1 dr).