Easy Access to Crystalline Indolines via Hydrogen Bond Transfer

Saira Khatoon, Aggeliki Vgenopoulou, Muhammad Moazzam Naseer, Bahareh Shirinfar, Benson M. Kariuki, Necmi Dege, Nisar Ahmed*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)

Abstract

Several indoline derivatives with specific geometries are biologically active and have inhibitor properties. Many indolines are a key part of natural products. Much attention has been focused on the development of synthetic routes for their easy access. Current synthesis depends largely on metal catalysis, iodine reagents, and Oxone. To date, no synthetic route has been established that is metal-free, reagent-free, and environmentally friendly and provides a base for green chemistry. Here, we report the first facile metal-free and reagent-free synthesis of indoline derivatives, which could potentially be influential in the design of new biologically active compounds. The synthesis proceeds through intramolecular amination between a urea nucleophile and unactivated alkene. The ring closure occurs in a few hours in the presence of pre-dried silica gel and gives good yields of indolines products, but in the absence of silica gel, the ring closure occurred overnight with stirring in dry solvent. An electron withdrawing group at the substituted aryl moiety of ureas increases the hydrogen bond donor ability of substrates that mediate the internal proton transfer at the terminal alkene and results in facile amination to give the indoline product with an “in plane” orientation of the carbonyl group and aromatic part of indoline framework. Such orientation in indolines is important for potent biological activities.

Original languageEnglish
Pages (from-to)1388-1392
Number of pages5
JournalJournal of Heterocyclic Chemistry
Volume56
Issue number4
DOIs
Publication statusPublished - 19 Apr 2019

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