Enantioselective Synthesis of C−N Axially Chiral N‐Aryloxindoles by Asymmetric Rhodium‐Catalyzed Dual C−H Activation

Abstract

The first enantioselective Satoh-Miura-type reaction is reported. Av ariety of CÀNa xially chiral N-aryloxindoles have been enantioselectively synthesized by an asymmetric rhodium-catalyzed dual C À Hactivation reaction of N-aryloxindoles and alkynes.H igh yields and enantioselectivities were obtained (up to 99 %yield and up to 99 %ee). To date,itisalso the first example of the asymmetric synthesis of CÀNa xially chiral compounds by such aC ÀHactivation strategy.

Rhodium‐Catalyzed Atroposelective Construction of Indoles via C−H Bond Activation

“…[13] Meanwhile, Wang disclosed Rh III -catalyzed [2+2+2] carboannulation between N-arylindolinones and alkyne. [14] Nevertheless, these very few reports [12][13][14] are limited to 6,6-biaryl synthesis due to reactivity challenge posed by employment of bulky directing group and/or coupling reagent. The rarity of axially chiral indoles via CÀH activation [9] is partially ascribed to the relatively low atropostability associated with pentatomic biarlys.…”

“…[2g,h, 9, 11l] Notably, Rh III -catalyzed CÀH activation has allowed facile access to a large array of chiral products. [9,[12][13][14][15] Inspired by Fagnous pioneering oxidative indole synthesis [16] and our own racemic system in 2010, [17] we aimed to apply C À H activation of anilines for atropomeric synthesis of Nisoquinolylindolines (Scheme 1 c). Despite related racemic reports, [16][17][18] control of enantioselectivity can be challenging because this requires conformational control of the isoquinoyl directing group prior to C-N reductive elimination.…”

Rhodium(III)‐Catalyzed Atroposelective Synthesis of Biaryls by C−H Activation and Intermolecular Coupling with Sterically Hindered Alkynes

“…[8] One notable example was recently reported by Wang in Rh III -catalyzed asymmetric synthesis of biaryls by [2+ +2+ +2] annulation of amides with two alkynes as ar esult of twofold C À H activation. [9] Despite increasing reports of asymmetric C À H activation catalyzed by chiral Rh III cyclopentadienyls, [4d, 10] examples of atroposelective synthesis of biaryls remain limited. [6d,e,7a, 9] Axial chirality can be delivered by restricting conformation of the coupling partner using an ascent arene ring generated by annulation with the adjacent p bond (Scheme 1c).…”

Enantioselective Twofold C−H Annulation of Formamides and Alkynes without Built‐in Chelating Groups

“…With this strategy, a number of chelated twofold C À H oxidative annulations have been achieved during the past decades. [3,4] Even most recently, two asymmetric examples of chelated twofold CÀH annulations were reported by the Wang [5] and Li groups, [6] who both used amides as chelating groups and chiral Cp-Rh complexes as efficient catalysts, achieving good to excellent yield and ee (Scheme 1 b). However, from the viewpoint of atom and step economy, non-chelated annulation would undoubtedly be a more attractive pathway because it avoids extra manipulations of chelating groups such as pre-installation and post-removal, thereby allowing the use more readily available substrates.…”