RESUMEN
We describe herein a gold-catalyzed three-component reaction of o-alkynylbenzaldehydes, aryldiazonium salts, and trimethoxybenzene. This process enables the one-pot formation of valuable isoindoles and 1,2-dihydrophathalazines. The regioselectivity of the reaction is dictated by the nature of the aryldiazonium salt. Noticeably, the reaction is performed at room temperature under mild conditions and tolerates a variety of functional groups on both the o-alkynylbenzaldehyde and the aryldiazonium salt. Experimental mechanistic studies suggest that it is catalyzed by arylAu(III) species.
RESUMEN
A one-pot diazotization/gold-mediated cyclization of 2-aminoaryl-3-arylpropargyl-benzenesulfonamides is described. After diazotization, Me2 SAuCl triggers an oxy- and/or chloroarylation of the alkyne moiety, resulting in the formation of 3-acylindoles and/or Z-3-(chloromethylene)indolines. Density Functional Theory (DFT) calculations show the significant energetic preference of both processes over an insertion pathway. Notably, a Z-3-(chloromethylene)indoline crystallized with [Cl-Au-Cl],- exhibiting Auâ â â H-C short contacts.
RESUMEN
In the last decade, aryldiazonium salts have attracted interest as coupling partners in cross-coupling reactions mediated by gold. Initially, the presence of a photocatalyst and a light source was needed to achieve gold oxidation with these electrophiles. However, recently, it has been shown that in some instances just heating, light irradiation, or the addition of certain bases and/or nucleophiles is enough. In this review, the transformations developed so far using aryldiazonium salts as electrophiles are summarized with special emphasis on mechanistic studies. The information gained by different authors, indicates that the specific steps of gold oxidation with aryldiazonium salts depends upon the activation mode of the diazonium salt.
RESUMEN
In recent years interest in the development of protocols that facilitate the oxidative addition of gold to access mild cross-coupling processes mediated by this metal has increased. In this context, we report herein that ascorbic acid, a natural and readily accessible antioxidant, can be used to accelerate the oxidative addition of aryldiazonium chlorides onto AuI . The aryl-AuIII species generated in this way, has been used to prepare 3-arylindoles in a one-pot protocol starting from anilines and para-, meta-, and ortho- substituted aryldiazonium chlorides. The mechanism underlying the oxidative addition has been examined in detail based on EPR analyses, cyclic voltammetry, and DFT calculations. Interestingly, we have found that in this protocol, the chloride atom induces the AuII /AuIII oxidation step.
RESUMEN
Alkynoic acids derived from salicylic acid and analogues undergo arylative cyclization with arenediazonium salts promoted by gold in the absence of external ligands. The reaction is thermally induced and proceeds even in the absence of light. A difference in regioselectivity has been found compared with that observed in the cycloisomerization process of the same type of compounds.
RESUMEN
Arenediazonium salts generated in situ from anilines have been found for the first time to efficiently oxidize [AuCl(L)] (L = SMe2, PPh3) complexes in DMSO as a solvent, under thermal conditions. The structure of the [AuArCl2(L)] complexes formed has been confirmed by X-ray diffraction analyses. These complexes have been used as intermediates, in a one pot cross-coupling reaction of anilines with silver acetylides.
RESUMEN
Alkenoic acids derived from salicylic acid and analogues undergo an unexpected oxidative cyclization process triggered by AgOAc leading to 4H-benzo[d][1,3]dioxin-4-ones. The process is affected by the substitution on the aryl and the allyl units.
RESUMEN
Phosphine-boronates R(2)P(o-C(6)H(4))B(OR')(2) have been evaluated as bifunctional organocatalysts for the Michael addition of malonate pronucleophiles to methylvinylketone. The presence of the Lewis acidic boron center adjacent to phosphorus significantly improves catalytic performance. Isolation and complete characterization of a key intermediate, namely a ß-phosphonium enolate, substantiate the role of the Lewis acidic moiety in the catalytic process.
Asunto(s)
Compuestos Alílicos/síntesis química , Oro/química , Compuestos Orgánicos de Oro/química , Acetatos/química , Compuestos Alílicos/química , Catálisis , Cationes/química , Ligandos , Estructura Molecular , Compuestos Orgánicos de Estaño/química , Paladio/química , Rodio/química , EstereoisomerismoRESUMEN
Oxidative cleavage with lead tetraacetate results in the synthesis of different oxygen heterocycles starting from the same unsaturated 1,2-diol of type I by tuning of the substitution pattern at the angular position. When this compound bears a functional substituent, such as an alkoxy, ester, alkenyl, or simply a hydrogen, more than one reaction pathway are in competition. The process allows for the selective formation of three different complex ring systems, by the appropriate choice of the angular substituent, leading to either a ring-expanded type 1, ring-retained type 2, or domino products 3.