The gold(I)‐catalyzed retro‐Buchner (decarbenation, retrocyclopropanation) reaction of 7‐substituted cycloheptatrienes has emerged as a safe and powerful alternative for the generation of gold(I) carbenes. These carbenes can cyclopropanate alkenes, take part in intramolecular reactions, or engage in higher cycloadditions with different partners, giving rise to a wide range of relevant structures. This review covers the developments made on the generation of gold(I) carbenes via decarbenation reactions, and the applications of these reactions in organic synthesis.

Mesityl gold(I) carbenes lacking heteroatom stabilization or shielding ancillary ligands have been generated and spectroscopically characterized from chloro(mesityl)methylgold(I) carbenoids bearing JohnPhos‐type ligands by chloride abstraction with GaCl₃. The aryl carbenes react with PPh₃ and alkenes to give stable phosphonium ylides and cyclopropanes, respectively. Oxidation with pyridine N‐oxide and intermolecular C−H insertion to cyclohexane have also been observed. In the absence of nucleophiles, a bimolecular reaction, similar to that observed for other metal carbenes, leads to a symmetrical alkene.

Chloromethylgold(I) complexes of phosphine, phosphite, and N‐heterocyclic carbene ligands are easily synthesized by reaction of trimethylsilyldiazomethane with the corresponding gold chloride precursors. Activation of these gold(I) carbenoids with a variety of chloride scavengers promotes reactivity typical of metallocarbenes in solution, namely homocoupling to ethylene, olefin cyclopropanation, and Buchner ring expansion of benzene.

Rh(iii)-catalyzed ortho-alkynylation of nitro-(hetero)arenes leads to a wide variety of alkynylated nitroarenes via a turnover-limiting electrophilic C–H ortho-metalation.

A novel synthesis of indanes and dihydronaphtalenes based on the intramolecular insertion into C(sp³)−H bonds of gold(I) carbenes generated by retro‐Buchner reaction (decarbenation) has been developed. Deuterium‐labeling and kinetic isotope effect experiments, DFT calculations, and generation of the proposed carbene intermediate from a well‐characterized gold(I) carbenoid support the involvement of a three‐center concerted mechanism for the C(sp³)−H functionalization process.

Chloromethylgold(I) complexes of phosphine, phosphite, and N‐heterocyclic carbene ligands are easily synthesized by reaction of trimethylsilyldiazomethane with the corresponding gold chloride precursors. Activation of these gold(I) carbenoids with a variety of chloride scavengers promotes reactivity typical of metallocarbenes in solution, namely homocoupling to ethylene, olefin cyclopropanation, and Buchner ring expansion of benzene.