Gold catalysis has, over the past decades, provided innovative organic transformations under mild conditions with high chemoselectivities. It receives steadily growing attention thanks to its wide synthetic applicability. The catalytically active form, [L n -Au] + , of ligated gold complexes, [L n -Au-Cl], is formed via halide abstraction. This is typically achieved by anion exchange upon the addition of an appropriate silver salt to the reaction mixture. Herein, an alternative silver-free route for gold activation is presented, making use of halogen bonding to promote halide abstraction. We demonstrate that a catalytic amount of a strong halogen bond donor efficiently activates both gold(I) and gold(III) catalysts. Following the reaction, both the catalyst and the activator are easily recovered. Importantly, this not only reduces the metal waste in a gold-catalyzed process but also enables its upscaling, possibly opening new avenues for its use in industrial settings. Gold is an expensive and limited resource, and its recyclability is of supreme importance. Based on systematic reaction kinetics, NMR spectroscopic, and computational investigations, we describe the mechanism of halogen bond-activated gold(I/III) catalysis using cyclopropanation as a model reaction. Our discovery paves the way for the development of gold-mediated transformations that allow recycling of the precious gold catalyst and that may thereby become useful also for the large-scale generation of complex molecules.

A gold-nitrone catalyzed [2 + 2 + 2] cyclotrimerization of 1,3-diarylpropargyl acetals into cyclohexylidene products (up to 74% yield) is reported. The trimerization is proposed to proceed through allenic intermediates via gold-catalyzed 1,3-alkoxy rearrangement. The presence of catalytic amounts of different nitrones, tuning of the Au(I) catalyst activity, was essential for controlled regio-/chemoselective cyclotrimerization. A linear nitrone-O-Au(I)-P coordination mode was shown (X-ray analysis) for a catalytic active phosphane-gold-nitrone complex, representing a group of Au(I) catalysts with specific properties.

Five pairs of novel chiral alcohol functionalised gold(I) and gold(III) NHC complexes derived from chiral amino alcohols, were synthesized and characterised (NMR, IR, HRMS). Single crystal X-ray diffraction data of...

The dual reactivity of gold-nitrone systems was studied. A series of novel Au(i)–nitrone complexes with specific catalytic properties were prepared.