Chiral Phosphoric Acid-Catalyzed Oxidative Kinetic Resolution of Indolines Based on Transfer Hydrogenation to Imines

Abstract

The oxidative kinetic resolution of 2-substituted indoline derivatives was achieved by hydrogen transfer to imines by means of a chiral phosphoric acid catalyst. The oxidative kinetic resolution was applicable to racemic alkyl- or aryl-substituted indolines, and the remaining indolines were obtained in good yields with excellent enantioselectivities.

The Golden Age of Transfer Hydrogenation

“…This transformation was realized by TH to imines such as 235 leading to the formation of the amine product 236 (Scheme 96). 737 This new method was successfully applied to the syntheses of various racemic alkyl-or aryl-substituted indolines, giving around 50% yields and >99% enantioselectivities.…”

Medium‐Ring Nitrogen Heterocycles through Migratory Ring Expansion of Metalated Ureas

“…Ther equisite 7-, 8-and 9membered ureas 14 were made either from ac ommercially available precursor (14 a,t wo steps from benzazepine) or by using reported procedures (14 b and 14 c [14] ). 2-Substituted indolines,p repared from the corresponding 2-substituted indoles, [16] were Scheme 2. [15] Chiral starting materials with substituents in the expanding ring underwent migratory ring expansion with complete diastereoselectivity (Scheme 5).…”

Palladium Catalyzed Asymmetric Three-Component Coupling of Boronic Esters, Indoles, and Allylic Acetates

“…18 Prior work has documented enantioselective functionalization of indoles through allylation and 1,4-conjugate addition; 16,17 likewise, chiral non-racemic indolines have been synthesized via asymmetric reduction 19 and kinetic resolutions. 20 Most existing methods introduce substituents only at C2 or C3, or they require substrates that are pre-functionalized at one or both of those positions. Herein, we report what is, to the best of our knowledge, the first enantioselective three component coupling that gives rise to indoles and indolines featuring concurrent C-C bond formation at both C2 and C3.…”