Pushing C–H amination to its limits fosters innovative synthetic solutions and offers a deeper understanding of the reaction mechanism and scope.

Scopolamine was synthesized using 6,7-dehydrotropine as a key intermediate. Rhodium-catalyzed [4 + 3] cycloaddition chemistry and a modified Robinson-Schöpf reaction

[3,3]‐Sigmatropic rearrangements represent powerful methods in the toolbox of synthetic organic chemists for the stereoselective construction of carbon–carbon as well as carbon–heteroatom bonds. Thus, the allyl cyanate/isocyanate rearrangement, although still underused for the preparation of allylamine derivatives, offers clear advantages over other similar methods. It usually occurs at or below ambient temperature with no need to use any metal catalyst, in a stereospecific way, and with a complete transfer of chirality. Moreover, combined with the high reactivity of the resulting isocyanates towards nucleophiles, this rearrangement gives access to various classes of compounds with wide structural and functional diversity. This microreview provides an overview of synthetic applications of this rearrangement since its discovery, with particular emphasis on its utility for the synthesis of complex nitrogen‐containing molecules such as natural products.

The synthesis of the first examples of a new class of iminosugars based on constrained spirocyclic scaffolds has been achieved via Rh-catalyzed C(sp(3))-H amination. In this process, the needed electronic control in securing high regioselectivity from substrates with a high density of activated C-H bonds was achieved by using a combination of activating and electron-withdrawing groups.

A stereodivergent synthesis of the first examples of 4-membered carbasugars has been achieved from vitamin C by way of an efficient intramolecular SmI2-mediated aldehyde-alkene coupling. In this key step, cylobutanes with four contiguous asymmetric centers are generated with a high level of stereocontrol.

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A synthetic route to a new class of conformationally constrained iminosugars based on a 5-azaspiro[3.4]octane skeleton has been developed by way of Rh(ii)-catalyzed C(sp(3))-H amination. The pivotal stereocontrolled formation of the quaternary C-N bond by insertion into the C-H bonds of the cyclobutane ring was explored with a series of polyoxygenated substrates. In addition to anticipated regioselective issues induced by the high density of activated α-ethereal C-H bonds, this systematic study showed that cyclobutane C-H bonds were, in general, poorly reactive towards catalytic C-H amination. This was demonstrated inter alia by the unexpected formation of a oxathiazonane derivative, which constitutes a very rare example of the formation of a 9-membered ring by way of catalyzed C(sp(3))-H amination. A complete stereocontrol could be however achieved by activating the key insertion position as an allylic C-H bond in combination with reducing the electron density at the undesired C-H insertion sites by using electron-withdrawing protecting groups. Preliminary biological evaluations of the synthesized spiro-iminosugars were performed, which led to the identification of a new class of correctors of the defective F508del-CFTR gating involved in cystic fibrosis.

A new tandem intramolecular azetidine ring-opening/closing cascade reaction affording spirocyclopropyl γ-lactams in high regio-and stereoselectivity is reported. The key step of the process is an S N 2-type ring-opening of TMSOTf-activated azetidine rings by silyl ketene acetals generated by