Gold-catalyzed decorations of arenes and heteroarenes with C–C multiple bonds

Abstract

Synthetic organic chemistry has been markedly affected by the booming of gold catalysis over the past decade. The renaissance of this coinage metal allowed unprecedented transformations to be realized in a highly selective manner and rendered "old chemistry" more accessible from a practical point of view. Particularly, organic compounds containing C-C multiple bonds benefited from the high carbophilicity of gold species, that opened access to a great chemical diversity through direct and selective π-electrophilic activations. Nowadays, the complexity of naturally occurring compounds based on functionalized aromatic frameworks continues to inspire and influence developments in synthetic chemistry. Furthermore, the ubiquitous presence of arene-based systems in pharmaceuticals, agrochemicals, and functional organic materials warrants the growing demand for mild, selective and sustainable synthetic routes to their preparation. In this context, although the peculiar aptitude of gold salts/complexes for interaction with aromatic compounds (auration process) has long been known, the direct catalytic gold decoration of arenes, has risen to prominence only recently. Here, the extensive use of electrophilic activation of C-C multiple bonds by gold species deserves a prominent mention, and the great strides made in the field over the last few years are described in this tutorial review.

A decarboxylative approach for regioselective hydroarylation of alkynes

“…The addition of an arene to an alkyne is one attractive route to these structures because of the commercial and synthetic availability of both reagents [1][2][3][4][5] . Such alkyne hydroarylations are more atom efficient and produce less salt waste than catalytic coupling of alkynes with pre-functionalized aromatic compounds (Fig.…”

“…In recent years, various transition-metal catalysts have been developed for alkyne hydroarylation via the formal activation of arene C-H bonds to form metal-aryl intermediates 4,5 . A number of these reported catalysts are Lewis acidic and cleave the C-H bond by electrophilic aromatic substitution, which is mechanistically analogous to the Friedel-Crafts reaction and leads to similar limitations on regioselectivity ( Fig.…”

Gold-Catalyzed Synthesis of 2-Sulfenylspiroindolenines via Spirocyclizations

“…Gold complexes are highly effective catalysts to trigger the addition of nucleophiles to alkynes [1][2][3][4][5][6]. Over the last few years, the functionalization of indoles using gold catalysis has stimulated very active research in the fields of catalysis and organic synthesis.…”

“…Over the last few years, the functionalization of indoles using gold catalysis has stimulated very active research in the fields of catalysis and organic synthesis. It is now well established that indoles can react with alkynes in an intramolecular fashion, upon exposure to Au(I) or Au(III) catalysts, via either their positions 2 or 3 [1,3,6]. When the alkyne is tethered to the 3-position of the indole and if position 2 is substituted, the compound will undergo dearomatizing cyclization [7][8][9], as illustrated by the conversion of the 2-methyltryptamine derivative 1 (X = Me) into the spiro-compound 2 [10] (Scheme 1).…”

The preference for dual-gold(i) catalysis in the hydro(alkoxylation vs. phenoxylation) of alkynes

“…[4][5][6][7][8][9][10] While most of these transformations are enabled by well-defined [Au(X)(L)] complexes (where L is typically a phosphine or N-heterocyclic carbene (NHC) ligand), it was assumed that the transformations catalysed by gold could be summarised by the simple activation of the substrate by one molecule of gold catalyst. However, more recently the importance of dual gold catalysis, by means of cycloisomerization reactions first proposed by Toste and Houk, 11 and Gagosz, 12 and later established for many synthetic protocols.…”