Redox Amination Scope of Benzylic Ketones with Indoline: Synthetic and Mechanistic Insights

Abstract

in Wiley Online Library (wileyonlinelibrary.com).Bi(NO 3 ) 3 ·5H 2 O-Catalyzed redox amination scope and mechanistic insights of benzylic ketones with indoline are discussed. The experimental results demonstrate that the formation of N-alkyl-substituted indole/indoline derivatives over typically competitive redox and reductive amination processes is depending upon the reaction condition for the benzylic ketones. Scheme 3. Proposed mechanism for the formation 6a and 10a. Scheme 4. Reactions of indoline (1, 1 equiv) with 1-indanone (5e) (1 equiv).Scheme 5. Isomerization attempts of 16. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Condensation of Indoline with Some 1,2‐ and 1,3‐Diketones

“…In a recent article, Tunge et al synthesized N ‐aryl‐1‐aminoindoles from indolines with different nitrosobenzenes via intermolecular redox amination (Scheme ) . Recently, we also investigated the redox amination potential of both enolizable cyclic and acyclic ketones and benzylic ketones with indoline . Our results showed that the formation of N ‐alkyl substituted indole/indoline derivatives over competitive redox and reductive amination processes depending on the reaction condition and ketones.…”

Condensation-Based Methods for the C–H Bond Functionalization of Amines

“…A similar reaction between indoline and benzylic ketones not only provides the corresponding N-alkylindoles, but also yields Nalkylindolines. 31 Tunge and coworkers reported a redox-amination reaction forming N-aryl-1-aminoindoles based on the condensation of indolines and nitrosobenzenes (Scheme 17). 32 The reaction is performed by adding nitrosobenzene slowly over a period of one hour to a mixture of indoline and 30 mol% of benzoic acid catalyst in toluene at 110 °C.…”

“…A similar reaction between indoline and benzylic ketones not only provides the corresponding N-alkylindoles, but also yields N-alkylindolines. 31…”

The synthesis of N‐benzoylindoles as inhibitors of rat erythrocyte glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase

“…Therefore, a great deal of attention has been given to develop effective, facile, and innovative synthetic strategies for the development of the indole chemistry. [16][17][18][19][20] The indole exhibits reactivity at the C-3 position against the electrophiles and generally forms the 3-substituent indole derivatives. An alternative method that utilizes indoline (4) for an easy and effective synthesis of N-substituted indoles was developed by Saracoglu and group.…”

“…An alternative method that utilizes indoline (4) for an easy and effective synthesis of N-substituted indoles was developed by Saracoglu and group. [16][17][18][19][20] The indole exhibits reactivity at the C-3 position against the electrophiles and generally forms the 3-substituent indole derivatives. Therefore, the synthesis of Nsubstituted indole derivatives, which form the main framework of many natural indole derivatives via reactions of indole, is quite difficult, and the reaction product is obtained with very low yields.…”