'Salen' along: the iridium(III)-salen complex 1 efficiently catalyzes the title reaction of 2-ethylbenzenesulfonyl azides to give five-membered sultams with high enantioselectivity. Other 2-alkyl-substitued substrates lead to five- and six-membered sultams with high enantioselectivity; the regioselectivity depends upon the substrate and the catalyst used. EDG=electron-donating group.

Scheme 1. Benzylic CÀH amination of indane with iridium-salen complexes as catalysts. TBDPS = tert-butyldiphenylsilyl. Figure 1. Ru(CO)-salen complexes. TMS = trimethylsilyl.

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Cyclic amine structures can be found in many biologically active compounds and their stereochemistry often has a significant effect on their biological activities. Enantioselective CÀN bond formation is a useful tool for synthesizing those compounds. Although various C À N bond-forming reactions are now known, C À H bond amination is highly atom efficient and it is of wide applicability because most organic compounds have CÀH bonds. Thus, regio-and stereoselective CÀH bond amination has attracted a growing amount of attention. [1] In addition, remarkable progress has recently been made in metal-catalyzed CÀH bond amination, particularly through metal nitrenoid insertion reactions. [2] Most of these C À H bond aminations, however, require Narenesulfonyliminophenyliodinane or related compounds to serve as the nitrene precursor and, furthermore, the atom efficiency of these particular reactions remains at an unsatisfactory level. Therefore, the establishment of a method for enantioselective C À H bond amination using an atom-efficient nitrene precursor such as an azide compound has become an increasingly common topic for research. [3] Seminal studies by Cenini and co-workers showed the potential of transitionmetal catalysis for CÀH bond amination using azide compounds. [4] Moreover, subsequent studies by Zhang and coworkers [5] and Driver and co-workers [6] demonstrated that intramolecular C À H bond amination catalyzed by a cobalt or an iridium complex is an efficient, though non-enantioselective, method of preparing heterocyclic compounds. Enantiopure sultams [7] have been used as chiral auxiliaries [8] and as key intermediates for the synthesis of HIV-1 reverse transcriptase [9] and COX-2 inhibitors. [10] An asymmetric version of the intramolecular C À H bond amination with arenesulfonyl azide [5a] could be an effective tool for the enantioselective synthesis of sultams, but the asymmetric version has not yet been reported.We recently reported that a ruthenium(CO)-salen complex catalyzed the enantioselective intermolecular allylic C À H bond amination using p-toluenesulfonyl azide with moderate to good enantioselectivity at room temperature (up to 80 % ee), albeit with low to moderate yields. [11] In contrast, we have recently demonstrated that iridium(III)-salen complexes are efficient catalysts for diastereo-and enantioselective carbenoid addition such as cyclopropanation, cyclopropenation, [12] and carbenoid C À H or Si À H bond insertion [13] using diazo compounds as the carbenoid precursors. Since diazo and azide compounds, and metal-carbenoid and nitrenoid intermediates are isoelectronic with one another, respectively, we expected that the iridium-salen complexes would serve as catalysts for asymmetric nitrenoid C À H bond insertion. Herein, we describe the enantioselective intramolecular C À H bond amination of sulfonyl azide compounds using an iridium-salen complex as the catalyst.Complexes 1-7 [14c] (Figure 1) were readily prepared from binol, an aryl halide, N,N-dimethylformamide, a diamine, and an ...

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