15 páginas, 19 figuras, 7 tablas.When N-unsubstituted indazoles, like indazole itself, reacted with 1-fluoro-2,4-dinitrobenzene or 1-chloro-2,4,6-trinitrobenzene, three products were obtained whose structures were determined by X-ray diffraction. Besides the two N-substituted nitroaryl derivatives, a third compound was obtained with the same molecular formula (C13H8N4O4) to which was assigned the structure of a derivative of benzotriazole N-oxide. With the combined use of crystallography, NMR and DFT calculations this reaction was studied with special stress on the mechanism of formation of the benzotriazole-N-oxide.This work was supported by the Spanish Ministerio de Economía y Competitividad (MAT2010-15094, Factoría de Cristalización–Consolider Ingenio 2010) and FEDER funding. We also thank the Ministerio de Ciencia e Innovación (Project No. CTQ 2009-13129-C02-02) and the Comunidad Autónoma de Madrid (Project MADRISOLAR2, ref. S2009/PPQ-1533) for continuing support. F. P. C. thanks the Spanish MICINN (Grants CTQ2010-16959 and Ingenio-Consolider CSD2007-00006) and the Basque Government (GV-EJ, Grant IT-324-07) for financial support.Peer reviewe
