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Don’t judge a nitro group by its electrophilia

Researchers from the Echavarren group have published in Chemical Science the paper “Rhodium-Catalysed ortho-Alkynylation of Nitroarenes,” where they present for the first time the nitro-directed C-H alkynylation of arenes catalysed by rhodium. The work has been highlighted as ChemSci’s Pick of the Week.

This new publication expands on the group’s research focused on the selective C-H alkynylation of functionalised molecules, and adds a plot twist: the methodology also works for a broad range of nitroarenes. The work details how the rhodium-catalysed ortho-alkynylation of nitroarenes happens through an electrophilic concerted metalation-deprotonation pathway, with perfect selectivity in the ortho position of the nitro group. Behaving as a “super pseudo-halogen” the nitro group allows to direct the alkynylation and perform a subsequent cross-coupling reaction.

The new protocol of alkynylation, reduction and cyclisation will allow for the efficient synthesis of important indoles from nitroarene feedstocks. In fact, the methodology expands the toolbox available to synthetic chemists, who will now be able to diversify more easily pharmaceutical and other biologically-relevant molecules.

Reference paper

Rhodium-Catalysed ortho-Alkynylation of Nitroarenes. Tan, E.; Montesinos-Magraner, M.; García-Morales, C.; Guillem Mayans, J.; Echavarren, A. M. Chem. Sci. 2021 DOI: 10.1039/D1SC04527J.