Véronique Michelet

Light‐mediated curing of terpene‐derived polymers generally depends on UV irradiation and photoinitiators. We report herein that environmentally friendly limonene‐ and carvone‐derived diepoxides cure with glutaric anhydride under white light through imidazole‐mediated catalysis, without conventional photoinitiators, to afford fully bio‐based thermosets. ¹ H NMR reveals a switch in ring‐opening selectivity relative to thermal curing, from predominant exo ‐epoxide opening under heating to preferential endo ‐epoxide activation under white light, evidencing a distinct light‐responsive pathway. The resulting novel thermosets are colorless, transparent and exhibit enhanced thermomechanical properties over thermally cured counterparts, with a Tg of 110°C, tensile strength of 42 MPa, and strain at break of 15%. This strategy is underexplored in terpene‐derived epoxy–anhydride systems and may broaden the scope of terpene‐based thermoset networks.

Light‐mediated curing of terpene‐derived polymers generally depends on UV irradiation and photoinitiators. We report herein that environmentally friendly limonene‐ and carvone‐derived diepoxides cure with glutaric anhydride under white light through imidazole‐mediated catalysis, without conventional photoinitiators, to afford fully bio‐based thermosets. ¹ H NMR reveals a switch in ring‐opening selectivity relative to thermal curing, from predominant exo ‐epoxide opening under heating to preferential endo ‐epoxide activation under white light, evidencing a distinct light‐responsive pathway. The resulting novel thermosets are colorless, transparent and exhibit enhanced thermomechanical properties over thermally cured counterparts, with a Tg of 110°C, tensile strength of 42 MPa, and strain at break of 15%. This strategy is underexplored in terpene‐derived epoxy–anhydride systems and may broaden the scope of terpene‐based thermoset networks.

Gold(I)‐catalyzed cycloisomerization reactions provide powerful access to structurally complex and 3D molecular frameworks from simple enyne precursors. Herein, we report a divergent gold‐catalyzed strategy for the synthesis of densely functionalized bicyclic and tricyclic polycyclic scaffolds from a common alkynyl ketone platform. Depending on the reaction conditions, solvent, and catalyst, the transformation proceeded through either a 6‐ endo ‐dig or a 5‐ exo ‐dig cyclization pathway, leading to distinct molecular architectures. Under selected conditions, bicyclo[3.3.1]nonane derivatives were obtained with high selectivity, while alternative conditions promote skeletal rearrangements delivering bridged tricyclic frameworks, including tricyclo[3.2.1.0 ^2,7 ]octanes and tricyclo[3.3.1.0 ^2,8 ]nonanes. According to literature mechanistic investigations, the involvement and evolution of key vinyl–gold and gold carbene intermediates may govern regioselectivity and product distribution. The role of solvent effects and substituent electronics in controlling pathway divergence was highlighted. This gold‐catalyzed divergent approach enabled rapid molecular complexity generation and provided efficient access to rigid, 3D polycyclic scaffolds of potential interest for medicinal chemistry and drug discovery applications.

This short review highlights recent advances in the enantioselective gold-catalyzed cycloisomerization of 1,6-enynes as an efficient strategy for accessing oxa- and aza-bicyclo[4.1.0]hept-4-enes as well as bicyclo[3.1.0] hexane derivatives. Emphasis is placed on the development of chiral gold catalysts and tailored substrate designs that enable high levels of chemo-, regio-, and stereocontrol despite the linear coordination geometry of gold(I). Mechanistic insights, including ligand effects and secondary interactions such as hydrogen bonding, are discussed to rationalize selectivity trends. The review also illustrates how these methodologies have enabled concise syntheses of biologically relevant molecules and hedonic compounds, underscoring the growing maturity and synthetic relevance of asymmetric gold catalysis.

A highly efficient gold(I)‐catalyzed enantioselective cycloisomerization of readily available 1,6‐oxygenated enynes is reported, enabling direct access to valuable 3‐oxabicyclo[4.1.0]hept‐4‐ene scaffolds with excellent enantiomeric excesses (up to >99% ee, 35 derivatives), in the presence of a chiral cationic Au(I) catalyst ((S)‐DTBM‐MeOBIPHEP(AuCl)₂ /AgOTf system) in toluene. This methodology uniquely combines high stereoselectivity with good to excellent yields for volatile substrates that have been challenging derivatives in the asymmetric cycloisomerization community. Notably, the resulting chiral bicyclic ethers serve as versatile intermediates for the synthesis of novel hedonic derivatives. A systematic investigation of their odor profiles reveals remarkable differences between enantiomers, demonstrating the profound impact of molecular chirality on olfactory perception.

A divergent synthesis of heterohexacyclic derivatives via a silver or gold-catalyzed cascade cycloisomerization/[3 + 2] or [2 + 2 + 1] cycloaddition in HFIP.

Gold catalysis has long been dominated by the ability of gold(I) to activate unsaturated systems as a carbophilic Lewis acid. However, recent advances have highlighted the significance of Au(I)/Au(III) redox transitions, unlocking new catalytic pathways. Among the strategies facilitating these oxidative processes, electrochemical anodic oxidation has emerged as a powerful tool. Despite its potential, the electrochemical properties of key gold complexes remain largely underexplored. In this study, we systematically investigate the oxidative behavior of a series of gold complexes using cyclic voltammetry. A comprehensive electrochemical scale is established, revealing that N ‐heterocyclic carbene (NHC)‐based gold complexes are among the least prone to oxidation, whereas phosphorylated ligands significantly enhance oxidizability. Within triphenylphosphine gold complexes, the nature of the X‐type anionic ligand plays a crucial role in determining oxidative behavior, a trend rationalized through density functional theory (DFT) calculations of the highest occupied molecular orbital (HOMO). Additionally, hemilabile P^N ligands dramatically facilitate oxidation, correlating with their ability to promote oxidative addition. These findings provide fundamental insights into the redox properties of gold complexes, offering valuable guidelines for the design of new gold‐catalyzed transformations.