Adrián Gómez-Suárez

Straightforward synthesis of [Au(NHC)X] (NHC = N-heterocyclic carbene, X = Cl, Br, I) complexes.

An improved protocol for the synthesis of [Au(NHC)X] (X = Cl, Br, I) complexes is reported. This versatile one-step synthetic methodology proceeds under mild conditions, in air, using technical grade solvents, is scalable and is applicable to a wide range of imidazolium and imidazolidinium salts.

Straightforward Synthetic Access to gem-Diaurated and Digold σ,π-Acetylide Species†

The advent of gold-mediated transformations has led to significant advances in organic synthesis. The majority of the synthetic/catalytic uses of gold catalysts rely on the welldocumented ability of monomeric gold complexes to activate C C multiple bonds or to form C Au s bonds which can be further functionalized. In contrast, the chemistry of dinuclear gold complexes, recently highlighted, remains relatively unexplored. Such complexes can activate organic molecules by the formation of either gem-diaurated or s,p-activated alkyne complexes (Figure 1). We believe that the reactivity of

Visible Light-Promoted Decarboxylative Di- and Trifluoromethylthiolation of Alkyl Carboxylic Acids

Described herein is a new and straightforward decarboxylative di- and trifluoromethylthiolation of alkyl carboxylic acids promoted by visible light. This approach enables the synthesis of biologically relevant alkyl SCF2H and SCF3 compounds from cheap and abundant carboxylic acids. The method is operationally simple, using irradiation from household light sources, and its mild reaction conditions make it tolerant of a range of functional groups. The strategy employs electrophilic phthalimide-derived di- and trifluoromethylthiolation reagents and exploits the ability of the imidyl radical to carry a radical chain.

Hydrophenoxylation of Alkynes by Cooperative Gold Catalysis

Over the past decade, the concept of cooperative or dual catalysis has emerged as an attractive and effective strategy to access unique reactivity and selectivity in synthetic organic chemistry. This type of catalysis has been shown in dual organo-catalyzed, organoand transition-metal-catalyzed, homobimetallic transition-metal-catalyzed and heterobimetallic catalyzed processes. Recently, it has also received increased attention in gold chemistry owing to the synthesis and isolation of dinuclear organogold species, such as gemdiaurated or s,p-diaurated acetylide complexes. These species were first proposed and later identified as key intermediates or catalyst reservoirs in gold-catalyzed reactions. We recently contributed to this area with the synthesis of dinuclear gold hydroxide species [{Au(NHC)}2(m-OH)][BF4] (1) (NHC = N-heterocyclic carbene), which can be easily prepared from commercially available [Au(NHC)(X)] (X = OH or Cl) complexes. Complexes 1 have been shown to be highly active catalysts for silverand acid-free goldcatalyzed transformations. We have also recently reported straightforward access to both gem-diaurated and s,p-diaurated acetylide species by reacting 1A (NHC = IPr = 1,3bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with aryl/vinyl boronic acids and terminal alkynes, respectively. In addition, complexes 1 exhibited particularly interesting catalytic properties. For example, during our studies of the goldcatalyzed nitrile hydration, the use of 1A afforded higher conversions to the desired amide than the gold monomer [Au(IPr)NTf2]. [8b] We have previously postulated that [{Au(NHC)}2(m-OH)][BF4] (1) could be considered as a combination of [Au(NHC)][BF4] (2) and [Au(NHC)(OH)] (3). [8] We believe that, under the appropriate reaction conditions, this equilibrium could be displaced, thus liberating a Lewis acid 2 and a Brønsted base 3 that could produce a synergistic effect leading to enhanced catalytic activity [Eq. (1)].

Synthetic routes to [Au(NHC)(OH)] (NHC = N-heterocyclic carbene) complexes

New procedures for the synthesis of [Au(NHC)(OH)] are reported. Initially, a two-step reaction via the digold complex [{Au(NHC)}(2)(μ-OH)][BF(4)] was probed, enabling the preparation of the novel [Au(SIPr)(OH)] complex and of its previously reported congener [Au(IPr)(OH)]. After further optimization, a one-step procedure was developed.

Accelerated Discovery in Photocatalysis using a Mechanism‐Based Screening Method

Herein, we report a conceptually novel mechanism-based screening approach to accelerate discovery in photocatalysis. In contrast to most screening methods, which consider reactions as discrete entities, this approach instead focuses on a single constituent mechanistic step of a catalytic reaction. Using luminescence spectroscopy to investigate the key quenching step in photocatalytic reactions, an initial screen of 100 compounds led to the discovery of two promising substrate classes. Moreover, a second, more focused screen provided mechanistic insights useful in developing proof-of-concept reactions. Overall, this fast and straightforward approach both facilitated the discovery and aided the development of new light-promoted reactions and suggests that mechanism-based screening strategies could become useful tools in the hunt for new reactivity.

Catalytic Access to Alkyl Bromides, Chlorides and Iodides via Visible Light‐Promoted Decarboxylative Halogenation

Herein is reported the catalytic, visible light-promoted, decarboxylative halogenation (bromination, chlorination, and iodination) of aliphatic carboxylic acids. This operationally-simple reaction tolerates a range of functional groups, proceeds at room temperature, and is redox neutral. By employing an iridium photocatalyst in concert with a halogen atom source, the use of stoichiometric metals such as silver, mercury, thallium, and lead can be circumvented. This reaction grants access to valuable synthetic building blocks from the large pool of cheap, readily available carboxylic acids.

Diverse Visible‐Light‐Promoted Functionalizations of Benzotriazoles Inspired by Mechanism‐Based Luminescence Screening

Three new visible-light-promoted functionalizations of benzotriazole substrates were discovered using a mechanism-based screening method. ortho-Thiolated, borylated, and alkylated N-arylbenzamide products were obtained under mild reaction conditions in a new denitrogenative synthetic approach to functionalized aniline derivatives. The functional group tolerance of the borylation reaction was further analyzed in the first application of an additive-based robustness screen in a photocatalytic transformation. All the functionalizations proceed via photocatalytically initiated chain mechanisms as indicated by determination of the reaction quantum yields and Stern-Volmer analyses.

Gold–Acetonyl Complexes: From Side-Products to Valuable Synthons

A new synthetic strategy was devised leading to the formation of complexes, such as [Au(IPr)(CH2 COCH3)]. The approach capitalizes on the formation of a decomposition product observed in the course of the synthesis of [Au(IPr)(Cl)]. A library of gold acetonyl complexes containing the most common N-heterocyclic carbene (NHC) ligands has been synthesized. These acetonyl complexes are good synthons for the preparation of numerous organogold complexes. Moreover, they have proven to be precatalysts in common gold(I)-catalyzed reactions.

A Switchable Gold Catalyst by Encapsulation in a Self‐Assembled Cage

Abstract Dinuclear gold complexes have the ability to interact with one or more substrates in a dual‐activation mode, leading to different reactivity and selectivity than their mononuclear relatives. In this contribution, this difference was used to control the catalytic properties of a gold‐based catalytic system by site‐isolation of mononuclear gold complexes by selective encapsulation. The typical dual‐activation mode is prohibited by this catalyst encapsulation, leading to typical behavior as a result of mononuclear activation. This strategy can be used as a switch (on/off) for a catalytic reaction and also permits reversible control over the product distribution during the course of a reaction.