Straightforward Access to Isoindoles and 1,2-Dihydrophthalazines Enabled by a Gold-Catalyzed Three-Component Reaction

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.

Revisiting aromatic diazotization and aryl diazonium salts in continuous flow: highlighted research during 2001–2021

Aryl diazonium salts play an important role in chemical transformations; however their explosive nature limits their applications in batch.

Key role of a π–π complex in diaryl cross-coupling between aryldiazonium salts and arylboronic acids using photosensitizer-free gold/photoredox catalysis

In a new mechanism for photosensitizer-free visible-light-mediated gold-catalyzed cross-coupling, the π–π complex between aryldiazonium salts and arylboronic acids acts as a photoinitiator.

The interplay of carbophilic activation and Au(I)/Au(III) catalysis: an emerging technique for 1,2-difunctionalization of C-C multiple bonds

Gold complexes have emerged as the catalysts of choice for various functionalization reactions of C-C multiple bonds due to their inherent carbophilic nature. In a parallel space, efforts to realize less accessible cross-coupling reactivity have led to the development of various strategies that facilitate the arduous Au(i)/Au(iii) redox cycle. The interplay of the two important reactivity modes encountered in gold catalysis, namely carbophilic activation and Au(i)/Au(iii) catalysis, has allowed the development of a novel mechanistic paradigm that sponsors 1,2-difunctionalization reactions of various C-C multiple bonds. Interestingly, the reactivity as well as selectivity obtained through this interplay could be complementary to that obtained by the use of various other transition metals that mainly involved the classical oxidative addition/migratory insertion pathways. The present review shall comprehensively cover all the 1,2-difunctionalization reactions of C-C multiple bonds that have been realized by the interplay of the two important reactivity modes and categorized on the basis of the method that has been employed to foster the Au(i)/Au(iii) redox cycle.

Selenocysteinyl electrophiles efficiently promote the formation of coumarin and quinolinone cores by 6-endo-dig cyclization

Efficient methods have been disclosed for the construction of nitrogen and oxygen containing heterocyclic systems attached to selenocysteine or selenoglutathione.

Gold-Catalyzed Addition of Carboxylic Acids to Alkynes and Allenes: Valuable Tools for Organic Synthesis

In this contribution, the application of gold-based catalysts in the hydrofunctionalization reactions of alkynes and allenes with carboxylic acids is comprehensively reviewed. Both intra- and intermolecular processes, leading respectively to lactones and linear unsaturated esters, are covered. In addition, cascade transformations involving the initial cycloisomerization of an alkynoic acid are also discussed.

Ascorbic Acid as an Aryl Radical Inducer in the Gold-Mediated Arylation of Indoles with Aryldiazonium Chlorides

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 Au^I . The aryl-Au^III 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 Au^II /Au^III oxidation step.

Mechanistic and asymmetric investigations of the Au-catalysed cross-coupling between aryldiazonium salts and arylboronic acids using (P,N) gold complexes

Aryldiazonium salts and arylboronic acids were coupled via three different pathways from (P,N)–AuCl complexes, with enantiomeric excesses up to 26%.