Easy access to crystalline indolines via hydrogen bond transfer

Khatoon, Saira, Vgenopoulou, Aggeliki, Naseer, Muhammad Moazzam, Shirinfar, Bahareh, Kariuki, Benson M. ORCID: https://orcid.org/0000-0002-8658-3897, Dege, Necmi and Ahmed, Nisar ORCID: https://orcid.org/0000-0002-7954-5251 2019. Easy access to crystalline indolines via hydrogen bond transfer. Journal of Heterocyclic Chemistry 56 (4) , pp. 1388-1392. 10.1002/jhet.3516

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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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Publisher:	Wiley
ISSN:	0022-152X
Date of First Compliant Deposit:	15 March 2019
Date of Acceptance:	22 January 2019
Last Modified:	07 Nov 2023 00:10
URI:	https://orca.cardiff.ac.uk/id/eprint/120747

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