Gaëlle Blond

We described herein two orthogonal tandem catalysis (OTC) systems that combine Au(III) and Rh(II) catalysts, demonstrating their excellent compatibility. The Au(III)-hydroacyloxylation/Rh(II)-cyclopropanation OTC enabled the synthesis of seven lactones bearing spirocyclopropane units. Additionally, the Au(III)-hydroiminoyloxylation/Rh(II)-cyclopropanation OTC yielded five dihydrooxazoles, also bearing spirocyclopropane architectures, thereby expanding the molecular diversity of these challenging heterocyclic scaffolds.

A MgBr ₂ ‐catalyzed (3 + 2) cycloaddition between N ‐thioacyl amidines and donor–acceptor cyclopropanes (DACs) has been developed, enabling the highly diastereoselective synthesis of polysubstituted 2‐amidino‐thiolanes in up to 92% yield and with dr values exceeding 99:1. The reaction proceeds under mild conditions and tolerates a broad range of DACs. The structures and relative configurations of the major diastereomers were established by single‐crystal X‐ray diffraction analysis of two representative derivatives. Further derivatization, including sulfur oxidation and an unexpected decarboxylative rearrangement to dihydrothiophenes, highlights the synthetic versatility of the products. DFT calculations suggest that the high diastereoselectivity arises from a lower‐energy cyclization transition state leading to the cis isomer. This work provides efficient access to sulfur‐containing heterocycles bearing the valuable amidine functionality.

We report a rhodium(II)‐catalyzed ring expansion of dihydro‐1,3‐thiazines with diazomalonates that provides tetrahydro‐1,4‐thiazepines bearing multiple stereocenters. The reaction proceeds through nucleophilic addition of the thiazine to the metallocarbene, catalyst release to form a sulfonium ylide, and rearrangement via an addition–elimination sequence to afford the thiazepine. A pronounced stereochemical effect arises for some cycloalkane‐fused thiazines: cis isomers efficiently furnish the corresponding cis ‐thiazepines, whereas trans isomers remain unreactive under standard conditions and react only at higher temperatures. Control experiments and density functional theory studies show that trans isomers coordinate more strongly to rhodium, thereby inhibiting the catalytic cycle. The synthetic versatility of the 1,4‐thiazepine scaffold is demonstrated by post‐transformations of the cyclic imine, including hydrolysis, reduction, and Krapcho decarboxylation.

We describe the first Au( i )-hydroacyloxylation/Rh( i )-hydroformylation orthogonal tandem catalysis giving access to aldehydes, alcohols and oximes.

Solar-driven plasmonic photocatalysis has emerged as a powerful tool to enhance chemical reactivity, improving the efficiency and selectivity in a large number of transformations. Plasmonic nanoparticles are often implemented in photocatalysis as colloidal dispersions but they face issues related to the reduced photoactivation of the metallic surface in concentrated solutions and poor long-term colloidal stability. To overcome these limitations, we introduce 3D plasmonic supercrystals created through the depletion- and evaporation-induced self-assembly of metal nanoparticles as novel heterogeneous plasmonic photocatalysts. They present large electromagnetic field enhancements associated to the formation of regular arrays of plasmonic hot spots, leading to improved chemical reactivities through the generation of hot charge carriers. To demonstrate this, we chose two challenging organic transformations, an oxidative polymerization and different C‒C cross-coupling reactions, that can be activated by modifying the chemical composition of the assemblies. Interestingly, the anisotropic shapes of the building blocks lead to the formation of 3D supercrystals exposing different crystalline facets. Importantly, by performing operando Surface-Enhanced Raman Spectroscopy at the single supercrystal level, we unveil the face-dependent reactivity of each individual plasmonic superstructure. Our combined experimental and theoretical approach provides with key insights into structure-function correlations and offers guidelines for the rational design of versatile supercrystal photocatalysts.

A series of 3‐allenyl benzo[b]thiophenes were synthesized through a gold(I)‐catalyzed domino reaction. The process consists in a 5‐endo‐dig cyclization with C−S bond formation and consecutive S‐to‐C propargyl migration via [3,3]‐sigmatropic Claisen rearrangement. With aryl substituents on both triple bonds of the substrate, subsequent intramolecular hydroarylation on the formed allenyl system led to 3‐indenyl benzo[b]thiophenes. From a substrate bearing a 3‐butynol moiety diverse fused O‐heterocycles have been obtained via intramolecular hydroalkoxylation. A gold‐mediated 1,3‐migration involving allenyl to propargyl rearrangement is also described. magnified image

A series of 1,4‐thiazepanes were synthesized using gold‐catalysis from 1,3‐aminothioethers having two or three carbon stereocenters. The process consists in a 7‐exo‐dig cyclization with C−S bond formation and concomitant allyl S‐to‐C migration, which occurs intramolecularly as demonstrated by a cross‐over experiment. X‐ray crystal‐structure analysis of one product confirmed the expected stereochemistry. Two examples of reactions, azide‐alkyne cycloaddition (CuAAC) and N‐alkylation, illustrate the potential post‐functionalization of the synthesized 1,4‐thiazepanes. Finally, the N‐propargyl 1,4‐thiazepanes underwent a sulfur‐assisted 1,6‐enyne cycloisomerization, which led through a 6‐exo‐dig cyclization to N,S‐heterobicyclo[4.3.1] systems with a bridgehead double bond. magnified image

. We report herein the synthesis of [7,5]‐fused bicyclic acetals, also named furooxepines through a gold(I)‐catalyzed domino reaction. During this transformation, two molecules of homopropargyl alcohol react together, in a sequence including an intramolecular hydroalkoxylation, condensation, a 1,6‐enyne cycloisomerization, acetalization and an isomerization. This gold(I)‐catalyzed domino reaction allow the formation of three bonds, two heterocycles and a tetrasubstituted carbon stereocenters in a one‐step operation with 100% atom economy. Post‐functionalizations allow the formation of tetrahydrofurans. magnified image