Taupo Volcanic Zone (TVZ) is a zone of intense volcanism and rifting associated with the subduction of the Pacific Plate beneath the continental crust of New Zealand's North Island. An image of the conductivity structure beneath the central part of the TVZ has been constructed using 2‐D inverse modeling of magnetotelluric data. A rapid increase in conductivity at a depth of 10 km beneath the TVZ, ∼3 km beneath the base of the seismogenic zone but well above the base of the quartzo‐feldspathic crust (∼16 km), is interpreted to mark the presence of an interconnected melt fraction (<4%) within the lower crust. Beneath the quartzo‐feldspathic crust the model shows a zone of increased conductivity on the eastern side of the TVZ consistent with an increased concentration of melt. At deeper levels the Pacific Plate is resistive compared with the overlying mantle.

A data-adaptive 2-D inversion scheme for magnetotelluric data, which simultaneously finds the smoothest model with the smallest misfit whilst solving for galvanic static shift parameters, is described. Trade-off parameters between data misfit, model roughness, and static shift norm are determined so as t o maximize the likelihood of the data on the assumption that static shifts have Gaussian distributions.

Two stable and optically active iridium-salen complexes were synthesized by introducing a tolyl or phenyl ligand at the apical position, respectively, via the S(E)Ar mechanism, and they were found to be efficient catalysts for cis-selective asymmetric cyclopropanation. The scope of the cyclopropanation was wide, and the reactions of not only conjugated mono-, di-, and trisubstituted olefins but also nonconjugated terminal olefins proceeded with high enantio- and cis-selectivity, even in the presence of a functional group such as an ether or ester. The utility of this cyclopropanation was demonstrated by a short step synthesis of 8-[(1R,2S)-2-hexylcyclopropyl]octanoate, isolated from Escherichia coli B-ATCC 11303, using the reaction as the key step.

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Nitrogen functional groups are found in many biologically active compounds and their stereochemistry has a profound effect on biological activity. Nitrene transfer reactions such as aziridination, C-H bond amination, and sulfimidation are useful methods for introducing nitrogen functional groups, and the enantiocontrol of the reactions has been extensively investigated. Although high enantioselectivity has been achieved, most of the reactions use (N-arylsulfonylimino)phenyliodinane, which co-produces iodobenzene, as a nitrene precursor and have a low atom economy. Azide compounds, which give nitrene species by releasing nitrogen, are ideal precursors but rather stable. Their decomposition needs UV irradiation, heating in the presence of a metal complex, or Lewis acid treatment. The examples of previous azide decomposition prompted us to examine Lewis acid and low-valent transition-metal complexes as catalysts for azide decomposition. Thus, we designed new ruthenium complexes that are composed of a low-valent Ru(II) ion, apical CO ligand, and an asymmetry-inducing salen ligand. With these ruthenium complexes and azides, we have achieved highly enantioselective nitrene transfer reactions under mild conditions. Recently, iridium-salen complexes were added to our toolbox.

'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.

C–H bonds are ubiquitous and abundant in organic molecules. If C–H bonds could be directly converted to desired functional groups in a chemo‐, site‐, and stereoselective manner, C–H functionalization would be a strong and useful tool for organic synthesis. Recent developments in catalytic and enzymatic chemistry have achieved highly sustainable and selective nitrene C–H insertion. Initially, C–H amination was inspired by model studies on enzymatic oxidation and used iminoiodinanes, nitrogen analogs of iodosobenzene, as nitrene precursors. Transition‐metal/iminoiodinane systems are well studied and established. These systems can directly introduce sulfonamide groups with excellent stereoselectivity, albeit with co‐production of iodobenzene as waste material. Fortunately, the atom economics of this methodology were improved by introducing highly sustainable nitrene sources such as azide compounds and 1,2,4‐dioxazol‐5‐one derivatives. In this review, we present the details of these developments with respect to their catalysts and nitrene sources.