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

Abstract

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.

Organocatalytic Enantioselective Friedel‐Crafts Alkylation Reactions of Pyrroles

“…Finally, in 2019, Zhang and coworkers reported the last example of FCA of pyrroles with vinyl iminium intermediates. This time, they employed a variety of 3‐vinylindole derivatives 97 as electrophiles and H 8 ‐BINOL‐derived imidodiphosphoric acid XXXVII as the catalyst [71] . This methodology gave access to a family of pyrrole‐containing 1,1,1‐triarylethanes 98 bearing a quaternary stereocenter in high to quantitative yields and with very good optical purities (Scheme 46, eq.…”

Recent Advances in Metal‐ and Organocatalyzed Asymmetric Functionalization of Pyrroles

“…Another representative example of enantioselective CÀ H functionalization of pyrroles 1 to 3-vinylindoles 176 as electro-philes was demonstrated by Zhang et al in 2019 (Scheme 64). [134] Under the influence of 5 mol% of chiral imidodiphosphoric acid C-41, several α-functionalized pyrrolesubstituted 1,1,1-triarylethanes 177 bearing all-carbon acyclic quaternary stereocenters were formed in moderate to excellent yield with good to high enantioselectivity. This catalyst system Scheme 62.…”

Efficient synthesis of polyfunctionalized carbazoles and pyrrolo[3,4-c]carbazoles via domino Diels–Alder reaction

“…Because indoles are readily available materials, the direct extension of indoles to carbazole skeletons has a great advantage [19][20][21][22][23][24][25][26][27]. Therefore, the Diels-Alder reaction of activated 2-vinylindolines or 3-vinylindolines with diverse dienophiles has become the most attractive strategy for the synthesis of carbazole deriv- atives [28][29][30][31][32][33][34][35][36][37][38][39][40]. In recent years, by using the one-pot domino synthetic strategy of in situ-generated 2-vinyl-or 3-vinylindolines and sequential Diels-Alder reaction with activated dienophiles, we have successfully developed several efficient synthetic protocols for diversely functionalized tetrahydrocarbazoles and the corresponding carbazole derivatives [41][42][43][44][45][46][47].…”