Synthesis 2024; 56(02): 312-328
DOI: 10.1055/a-2193-4804
paper

Benzoxazole or Benzothiazole as an Innate Directing Group for Palladium- and Ruthenium-Catalyzed Complementary C–H Arylation: Functionalization of Biorelevant Heterocyclic Scaffolds

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Firojkhan Rajekhan Pathan
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M.M., S.S., L.S., and F.R.P. thank the Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Govt. of India for their fellowships.


Abstract

The benzoxazole and benzothiazole moieties were used as innate directing groups for Pd(II)- and Ru(II)-catalyzed C–H arylation of the biorelevant heterocycles 2-arylbenzoxazole and 2-arylbenzothiazole with diverse iodoarenes; palladium and ruthenium catalysis could be used complementarily. The use of σ-donor ligands, such as N,N-dimethylacetamide in the Pd(II) catalytic cycle, and σ-donor/π-acceptor ligands, such as PPh3 in the Ru(II) catalytic cycle, enhanced the arylation rate significantly and was governed by the C–H acidity of the C2-aryl ring of the 2-arylbenzoxazole or 2-arylbenzothiazole. These approaches have a broad substrate scope with respect to coupling partners, to accommodate electron-neutral, electron-rich, as well as electron-deficient iodoarenes; the C2-aryl unit of the 2-arylbenzoxazole or 2-arylbenzothiazole exhibited a high degree of site selectivity at the ortho C–H position, affording only monoarylated derivatives in decent yields; the reactions are functional-group-tolerant and applicable to gram-scale production.

Supporting Information



Publication History

Received: 06 September 2023

Accepted after revision: 17 October 2023

Accepted Manuscript online:
17 October 2023

Article published online:
13 November 2023

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