Thianthrenium Ylides Enable Carbene Transfer for Cyclopropanation

A new methodology has been established for the generation and transfer of metal carbenes, utilizing thianthrenium ylides as a versatile platform. This breakthrough, published online in Nature on September 30, 2026, with the digital object identifier 10.1038/s41586-026-11108-z, opens up new avenues for synthetic organic chemistry, particularly in the construction of complex molecular architectures. The research demonstrates that thianthrenium ylides can serve as a general precursor for various carbene-mediated transformations, including cyclopropanation, sigma-bond insertion, and sigmatropic rearrangements. This broad applicability suggests a significant advancement in the field of organometallic chemistry and catalysis.

Cyclopropanation, a key reaction for forming three-membered carbon rings, is a fundamental process in the synthesis of pharmaceuticals, agrochemicals, and materials. Traditional methods often rely on stoichiometric or catalytic amounts of transition metals, which can be expensive, toxic, or difficult to remove from the final product. The developed method using thianthrenium ylides offers a potentially more sustainable and efficient alternative by providing a controlled release of carbenes. The ylides act as stable precursors that can be activated under specific conditions to generate reactive carbene species. These carbenes then undergo the desired transformations with various substrates, leading to the formation of cyclopropane rings with high efficiency and selectivity.

Beyond cyclopropanation, the research highlights the utility of thianthrenium ylides in other important carbene reactions. Sigma-bond insertion, where a carbene inserts into a carbon-hydrogen or carbon-carbon single bond, is a powerful tool for C-H functionalization and the construction of new carbon-carbon bonds. Sigmatropic rearrangements, a class of pericyclic reactions involving the migration of a sigma bond accompanied by a rearrangement of pi bonds, are also facilitated by the carbene intermediates generated from these ylides. The ability of a single platform to mediate such a diverse range of reactions underscores its potential as a general synthetic tool.

The thianthrenium ylide system is characterized by the presence of a thianthrene moiety, a sulfur-containing heterocyclic compound, linked to a carbanionic center. This unique structure allows for the stabilization of the ylide while also enabling facile cleavage of the bond between the sulfur atom and the carbanionic carbon upon activation, leading to the generation of the carbene. The specific conditions for activation, such as the choice of catalyst or reaction temperature, can be tailored to control the reactivity and selectivity of the carbene species. This level of control is crucial for achieving high yields and minimizing unwanted side reactions in complex synthetic sequences. The implications of this work extend to the development of new catalytic systems and more streamlined synthetic routes for valuable chemical compounds.