A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of
Luca Scapinello1, Angelo Maspero1, Stefano Tollari1
1Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell'Insubria.
Abstract:
We introduced a regioselective and atom-economical procedure for the synthesis of 3-substituted indoles by annulation of nitrosoarenes with ethynyl ketones. The reactions were carried out achieving indoles without any catalyst and with excellent regioselectivity. No traces of 2-aroylindole products were detected. Working with 4-nitronitrosobenzene as starting material, the 3-aroyl-N-hydroxy-5-nitroindole products precipitated from the reaction mixtures and were isolated by filtration without any further purification technique. Differently from the corresponding N-hydroxy-3-aryl indoles that, spontaneously in solution, give dehydrodimerization products, the N-hydroxy-3-aroyl indoles are stable and no dimerization compounds were observed.
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