The nucleophilic iron complex Bu N[Fe(CO) (NO)] (TBA[Fe]) catalyzes the direct intramolecular amination of unactivated C(sp )-H bonds in alkylaryl azides, which results in the formation of substituted indoline and tetrahydroquinoline derivatives.

The activation of diazo compounds by nitrogen extrusion in the presence of transition-metal complexes is a convenient method for the transfer of a carbene to an organic substrate in, for example, [2+1] cycloadditions with olefins [1] or carbonyl compound [2] to give three-membered-ring compounds, or in reactions with electron-rich heteroatoms like sulfur, [3] phosphorus, [4] and nitrogen [5] to generate ylides. [6] In general, these types of reactions are catalyzed by oxidized transition-metal complexes based upon copper, [1, 7] rhodium, [5a-d] ruthenium, [8] palladium, [9] cobalt, [10] iron, [4,11] and silver. [12] In the initial step the metal center is reduced by nucleophilic addition of the diazo compound. The subsequent back-donation of an electron from the metal to the carbon atom with concomittant release of nitrogen results in the formation of the metal-carbon double bond [Eq. (1) in Figure 1].In contrast, the corresponding activation of stabilized, electron-poor diazo compounds by nucleophilic and hence electron-rich transition-metal complexes is unprecented. From a mechanistic point of view the metal center would add into the C = N bond of the diazo compounds followed by an electron back-donation with release of nitrogen and formation of the metal-carbon double bond [Eq.(2), Figure 1]. [13] With respect to the oxidation state of the metal center both mechanistic manifolds are redox-neutral; how-ever, the latter mechanism might favor the undesired carbene dimerization to the corresponding olefins.We were wondering whether the electron-rich ferrate complex Bu 4 N[Fe(CO) 3 (NO)] (TBAFe), in which the metal center has a formal oxidation state of ÀII and which has been investigated in detail by us and others over the past years, [14] might be able to activate diazo compounds for carbenetransfer reactions. Herein we report the successful realization of this concept in various catalytic transformations including Wittig-type olefinations, [15] the insertion into heteroatomhydrogen bonds, [16] and the Doyle-Kirmse reaction. [17] Since to the best of our knowledge the activation of diazo compounds by reduced metal catalysts has not been reported, we initiated our studies by investigating the carbene transfer using ethyl diazoacetate (6, EDA) as the electrophilic carbene precursor in different model reactions. Apart from its electronic properties, which could result in an increased reactivity toward electron-rich metal complexes, this diazo compound is stable and commercially available in pure form. Gratifyingly, a system consisting of catalytic amounts of TBAFe and stoichiometric amounts of 6 showed good reactivity in 1,2-dichloroethane (Scheme 1).Both the insertion into SÀH and NÀH bonds as well as the transfer of the carbenoide to electron-rich heteroatoms with intermediate formation of an ylide (olefination [18,19] and Doyle-Kirmse reaction) were accomplished under almost Figure 1. Mechanistic model for the decomposition of diazo compounds by electrophilic or nucleophilic metal catalysts.Scheme 1. TBAFe-cat...

The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) catalyzes the direct intramolecular C-H amination of α-azidobiaryls and (azidoaryl)alkenes into the corresponding carbazoles and indoles, respectively, under mild conditions and with low catalyst loadings. These features and the broad functional-group tolerance render this method a particularly attractive alternative to established noble-metal-based procedures.

An in‐depth study of carbene transfer reactions into polar X−H‐bonds catalyzed by the nucleophilic Fe‐complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) is presented. Whereas alcohols are unreactive, thiols and secondary amines are reactive, silanes showed modest activities. Hammett correlations indicate the presence of an X−H‐acidity dependent mechanistic dichotomy.

A defined NHC-Fe−S complex proved to be an efficient catalyst for the selective hydrosulfenylation of α,βunsaturated ketones or vinylnitriles. A wide range of different aliphatic thiols were transferred in this atom-economic reaction into the corresponding thioethers. Mild reaction conditions, equimolar amounts of substrates, low catalyst loadings, and mild reaction conditions are characteristic for this transformation.