Three decades of unveiling the complex chemistry of C-nitroso species with computational chemistry

C-Nitroso species are characterized by a unique nitrogen–oxygen combination located next to a carbon backbone, which confers them a unique ambiphilic and high reactivity towards nucleophilic, electrophilic but also radical species. Although this ambivalence can be seen as a strong asset for developing versatile synthetic aminohydroxylation and/or hydroxylamination processes mainly through nitroso Diels–Alder, nitroso ene, and nitrosoaldol reactions, it also contributes to complex optimization and rationalization arising from the many competitive pathways, that is, the occurrence of regioisomers and stereoisomers, as well as dimerization and tautomerization side-reactions. Complex reactivity profiles are usually seen by synthetic organic chemists as major hurdles to overcome, despite the armada of analytical and purification methods available to them, and hence to achieve selective and exploitable developments of such reactions. The rise of computational chemistry and resources has certainly changed their perspectives, since it provides a very different angle to gather insights on intrinsic properties, reactivity, and mechanisms. In silico chemistry also provides a robust alternative to time and resource-consuming synthetic work and can therefore contribute to alleviate wasteful preparations by guiding the chemist toward the best combination of reagents to achieve high selectivity and yield. The synergistic combination of synthetic organic chemistry and computational chemistry, within the specific context of the complex chemistry of C-nitroso species, is discussed in this work. This review aims at giving an overview of the molecular and chemical properties obtained through computational chemistry as an enabling support for the rationalization and optimization of reactions relying on ambiphilic C-nitroso species over the 3 last decades. It provides clear, concise, and illustrated guidelines for the synthetic chemist in search of inspiration through computations.