FULL PAPER DOI: 10.1002/ejoc.200700931 Reactions of Arenediazonium o-Benzenedisulfonimides with Aliphatic Triorganoindium Compounds Margherita Barbero, [a] Silvano Cadamuro, [a] Stefano Dughera,* [a] and Giovanni Ghigo* [a] Keywords: Indium / Amines / Diazo compounds / Nucleophilic addition / Density functional calculations The reaction of various arenediazonium o-benzenedisulfon- imides with aliphatic triorganoindium compounds is de- scribed. Surprisingly, with triethyl- or tributylindium we ob- tained N-ethyl- or N-butylanilines, respectively. This is the first case in which, at least formally, the reactive site of a diazonium salt is the nitrogen atom directly bonded to the aromatic ring. In contrast, with trimethylindium we obtained only formaldehyde (aryl)hydrazones. In order to explain the difference between trimethyl- and triethylindium we have proposed some reaction mechanisms, supported by detailed density functional (DFT) calculations. The possible role of di- azene/hydrazone tautomerism initially assumed was dis- Introduction Recently we reported the reactions between arenediazon- ium o-benzenedisulfonimides and aromatic triorganoind- ium compounds; depending on the reaction conditions, it was possible to obtain two different products, biaryls or diaryldiazenes. [1] As a follow-up of previous research, in this paper we re- port a study of the reactions of arenediazonium o-benzene- disulfonimides 1 with aliphatic triorganoindium com- pounds [triethyl- (2) and tributylindium (3)]. To our great surprise, an aqueous treatment of the reaction mixtures gave, in good yields, N-ethyl- 4 and N-butylanilines 5, respectively, and not the expected diazenes. Furthermore, with trimethylindium (10) we obtained formaldehyde (aryl)- hydrazones 11 and not the expected N-methylanilines (Scheme 1). Therefore, in order to explain these unusual results, we have proposed some reaction mechanisms, sup- ported by detailed density functional (DFT) calculations. Currently, the main method of preparing indium organo- metallics involves the reaction of indium(III) chloride with readily available lithioorganic compounds or Grignard rea- gents. In this way it is possible to obtain a large variety of [a] Dipartimento di Chimica Generale ed Organica Applicata dell’Università, Corso M. d’Azeglio 48, 10125 Torino, Italy Fax: +39-011-6707642 E-mail: stefano.dughera@unito.it giovanni.ghigo@unito.it Supporting information for this article is available on the WWW under http://www.eurjoc.org or from the author. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Org. Chem. 2008, 862–868 862 carded and therefore three mechanisms for the key step (nu- cleophilic addition of the trialkylindium to the N=N double bond of diazene) were studied. For the favoured mechanism there is a difference in the energy barriers of 2 kcal mol –1 be- tween the reactions with trimethyl- and triethylindium. This difference is explained on the basis of the different C–In bond energies in the two organometallics and it is assumed to be enough to explain their different behaviour under the experimental conditions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) Scheme 1.