The development of catalytic chemical processes that enable the revalorization of nitrous oxide (N2O) is an attractive strategy to alleviate the environmental threat posed by its emissions1–6. Traditionally, N2O has been considered an inert molecule, intractable for organic chemists as an oxidant or O-atom transfer reagent, owing to the harsh conditions required for its activation (>150 °C, 50‒200 bar)7–11. Here we report an insertion of N2O into a Ni‒C bond under mild conditions (room temperature, 1.5–2 bar N2O), thus delivering valuable phenols and releasing benign N2. This fundamentally distinct organometallic C‒O bond-forming step differs from the current strategies based on reductive elimination and enables an alternative catalytic approach for the conversion of aryl halides to phenols. The process was rendered catalytic by means of a bipyridine-based ligands for the Ni centre. The method is robust, mild and highly selective, able to accommodate base-sensitive functionalities as well as permitting phenol synthesis from densely functionalized aryl halides. Although this protocol does not provide a solution to the mitigation of N2O emissions, it represents a reactivity blueprint for the mild revalorization of abundant N2O as an O source.

Transition metal-catalyzed transformations of vinyldiazo compounds have become a versatile tool in organic synthesis. Although several transition metals have been investigated for this purpose, this field has been mainly dominated by dirhodium catalysts. Remarkable levels of chemo-, regio-, diastereo- and enantioselectivity have been reached in some of these rhodium-catalyzed transformations. In the last few years coinage metals have also emerged as useful catalysts in transformations involving vinyldiazo compounds. In some cases, highly efficient catalyst-dependent protocols arising from divergent mechanistic pathways have been reported. In this Personal Account, we aim to showcase recent advances in metal coinage catalyzed transformations of vinyldiazoacetates, an exciting field of research to which our group has actively contributed in the last few years.

The Lewis (or Brønsted) acid‐catalyzed reaction of 2‐aryl‐N‐sulfonyl aziridines with ferrocene and ruthenocene provided new amino‐functionalized metallocene derivatives arising from a regioselective ring opening of the aziridine. The functionalized metallocene derivatives available by this methodology are suitable precursors for the stereoselective synthesis of metallocene analogues of the relevant tetrahydroisoquinoline motif by a Pictet‐Spengler type reaction. These isoquinoline analogues are also accessible by a TfOH‐catalyzed three‐component reaction of 2‐aryl‐N‐sulfonyl aziridines, ferrocene (or ruthenocene) and formaldehyde.

An efficient activator-free protocol for the coupling of ohydroxybenzyl alcohols and azoles in water has been developed. Thi s C-N bond formation process is supposed to proceed through an orthoquinone methide intermediate. A broad range of o-hydroxybenzyl alcohols including those having alkenyl and alkynyl functionalities i s compatible w ith this protocol. In most cases, the products are isolated in good to excellent yields w ithout chromatographic purification. Preliminary results demonstrated that this methodology can be also used for the generation and trapping of the isomeric para-quinone methide intermediates.

The marriage of heterocyclic compounds with ferrocene has proven to be an extremely fruitful field of research. In fact, in the last years, several ferrocene-embedded heterocyclic compounds have been reported. In some cases, the synergistic combination of the properties of the heterocyclic and metal-lacyclic motifs provides to the fused systems interesting applications. This Review summarizes the major advances in the synthesis of ferrocene-fused nitrogen heterocyclic compounds and their applications, particularly in asymmetric catalysis.