The Ir(I)−butadiene complex TpMe2Ir(η4-CH2C(Me)C(Me)CH2) (1) (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) reacts with ≥3 equiv of DMAD (RC⋮CR, R = CO2Me) in CH2Cl2 at 60 °C, in the presence of adventitious water, with formation of the iridacycloheptatriene (2), by the oxidative coupling of three molecules of DMAD in the metal coordination sphere. In a related process, TpMe2IrPh2(N2) (4) gives two benzoannelated iridacycloheptatrienes, the symmetrical species (5) and the unsymmetrical one (6). The water ligand in these complexes is labile, and derivatives substituted with CO, PMe3, and NCMe have been obtained. 2, 5, and 6 react, at 25 °C, with oxo-transfer oxidizing reagents such as tBuOOH with formation of the keto-metallabicyclic products 7−9, which result from the selective oxo attack to the γ,δ-CC double bond, irrespective of this being of the benzo or the (R)CC(R) type. In the latter case, further oxidation takes place with tBuOOH, at ambient temperature, with formation of an iridabenzene (11) and an iridanaphthalene (12) (with five and three electron-withdrawing CO2Me substituents, respectively) in which the carboxylate MeO2CCO2 - ligand completes the metal coordination sphere. Interestingly, substitution of this group by OH- or MeO- allows the formation of Jackson−Meisenheimer complexes, reflecting the inherent aromaticity of these electron-deficient metalloaromatics. Finally, the hydrogenation of the iridacycloheptatrienes has been studied. All new compounds have been fully characterized by microanalysis, IR and NMR spectroscopies, and, in some cases, single-crystal X-ray diffraction studies.

Substituted imines, alpha,beta-unsaturated imines, substituted secondary amines, and beta-amino carbonyl compounds have been synthesized by means of new cascade reactions with mono- or bifunctional gold-based solid catalysts under mild reaction conditions. The related synthetic route involves the hydrogenation of a nitroaromatic compound in the presence of a second reactant such as an aldehyde, alpha,beta-unsaturated carbonyl compound, or alkyne, which circumvents an ex situ reduction process for producing the aromatic amine. The process is shown to be highly selective towards other competing groups, such as double bonds, carbonyls, halogens, nitriles, or cinnamates, and thereby allows the synthesis of different substituted nitrogenated compounds. For the preparation of imines, substituted anilines are formed and condensed in situ with aldehydes to provide the final product through two tandem reactions. High chemoselectivity is observed, for instance, when double bonds or halides are present within the reactants. In addition, we show that the Au/TiO2 system is also able to catalyze the chemoselective hydrogenation of imines, so that secondary amines can be prepared directly through a three-step cascade reaction by starting from nitroaromatic compounds and aldehydes. On the other hand, Au/TiO2 can also be used as a bifunctional catalyst to obtain substituted beta-amino carbonyl compounds from nitroaromatics and alpha,beta-unsaturated carbonyl compounds. Whereas gold sites promote the in situ formation of anilines, the intrinsic acidity of Ti species on the support surface accelerates the subsequent Michael addition. Finally, two gold-catalyzed reactions, that is, the hydrogenation of nitro groups and a hydroamination, have been coupled to synthesize additional substituted imines from nitroaromatic compounds and alkynes.