Chemo- and regio-selective amidation of indoles with isocyanates using borane Lewis acids

Dasgupta, Ayan, Guerzoni, Michael G., Alotaibi, Nusaybah, van Ingen, Yara, Farshadfar, Kaveh, Richards, Emma ORCID: https://orcid.org/0000-0001-6691-2377, Ariafard, Alireza and Melen, Rebecca L. ORCID: https://orcid.org/0000-0003-3142-2831 2022. Chemo- and regio-selective amidation of indoles with isocyanates using borane Lewis acids. Catalysis Science & Technology 12 (19) , pp. 5982-5990. 10.1039/D2CY01441F

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Abstract

The efficacy of boron-based catalysts has drawn considerable attention from the scientific community due to their relatively low toxicities and high selectivities. Formation of a new carbon–carbon or carbon–nitrogen bond to generate an amide/urea functionality using mild, catalytic reaction protocols has always been an important challenge, as functionalised amides and urea derivatives are important scaffolds in medicinal chemistry. Herein we report a facile and mild catalytic reaction protocol towards the amidation of N-methyl indoles/pyrroles (17 examples, yields up to 58%) using B(C6F5)3 (30 mol%). Moreover, our investigation revealed that although catalytic amounts of B(C6F5)3 (10 mol%) are efficient towards the N-carboxamidation of unprotected indoles, catalytic BCl3 (5 mol%) is capable of producing near quantitative yields of the N-carboxamidation products (21 examples, yields up to 95%). In contrast with previous literature reports, the reaction between 2-(alkynyl)anilines and aryl isocyanates using catalytic BCl3 (5 mol%) afforded N–H inserted products (9 examples, yields up to 71%) chemo-selectively as opposed to the intramolecular hydroamination product. Comprehensive DFT studies have been undertaken to understand the mechanistic details of the N–H functionalisation of indoles.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry Cardiff Catalysis Institute (CCI)
Publisher:	Royal Society of Chemistry
ISSN:	2044-4753
Funders:	EPSRC, Leverhulme Trust
Date of First Compliant Deposit:	6 September 2022
Date of Acceptance:	18 August 2022
Last Modified:	18 Aug 2023 00:13
URI:	https://orca.cardiff.ac.uk/id/eprint/152384

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