Hydroamination/hydroarylation

A-vinylindoles took place. Moreover, the gold-catalyzed cyclization of 2-alkynylanilines can be combined with a gold-catalyzed Michael addition to enones, which afforded 3-alkylated indoles with good yield. Gold-catalyzed hydroamination/hydroarylation cascades of polyenyne-substituted anilines leading to condensed aromatics have been described recently. ... 

Che has reported the tandem hydroamination/hydroarylation of aromatic amines wirh terminal alkynes to form dihydroquinolines in which 1 equiv of aniline combines with 2 equiv of alkyne [23]. For example, reaction of 3-methoxyanilme with pheny-lacetylene (5 equiv) and a catalytic 1 1 mixture of the gold(I) N-heterocydic carbene complex (IPr)AuCl (IPr= l,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidine) and AgOTf at 150 °C under microwave irradiation led to isolation of dihydroquinoline 21 in 82 % yield (Eq. (11.15)). Alternatively, reaction of o-acetylaniline with pheny-lacetylene catalyzed by a mixture of (IPr)AuCl and AgOTf at 150 °C led to isolation of the quinoline derivative 22 in 93% yield via incorporation of a single equivalent of alkyne (Eq. (11.16)). Arcadi has reported the gold(IlI)-catalyzed hydroamination/ hydroarylation of 2-alkynylanilines with a,p-enones to form C3-alkyl indoles [24]. As an example of this transformation, treatment of 2-(phenylethynyl)aniline with 4-phenyl-3-buten-2-one and a catalytic amount of sodium tetrachloroaurate dihydrate in ethanol at 30°C formed 1,2,3-trisubstituted indole 23 in 88% yield (Eq. (11.17)). 

Scheme 15.121 Synthesis of multicyclic N-heterocycles via tandem hydroamination /hydroarylation.

Scheme 7.67 Tandem hydroamination-hydroarylation-transfer hydrogenation reaction catalysed by gold catalysis and chiral phosphoric acid...

NHC-Au catalysts, in line with results obtained in hydration and hydroalkox-ylation reactions vide supra], proved to be highly efficient in this field, and the inter- and intramoleeular hydroamination of various alkenes, allenes, and alkynes were reported with a number of NHC-Au complexes. In 2008, Bertrand and co-workers disclosed an extremely efficient alkyne and allene hydroamination catalyzed by a CAAC-Au eomplex (Scheme 11.15). These peculiar NHCs allowed for the challenging use of ammonia and proved useful in a hydroamination/hydroarylation cascade leading to 1,2-dihydroquinolines. The same authors subsequently employed a similar method to perform the addition of hydrazine on alkynes in an intermoleeular manner. ... 

Abstract The use of A-heterocyclic carbene (NHC) complexes as homogeneous catalysts in addition reactions across carbon-carbon double and triple bonds and carbon-heteroatom double bonds is described. The discussion is focused on the description of the catalytic systems, their current mechanistic understanding and occasionally the relevant organometallic chemistry. The reaction types covered include hydrogenation, transfer hydrogenation, hydrosilylation, hydroboration and diboration, hydroamination, hydrothiolation, hydration, hydroarylation, allylic substitution, addition, chloroesterification and chloroacylation. 

Some of the hydroarylation product is also observed substituted anilines afford the two products to varying degrees (Equation (15)). The closely related rhodium complexes [Rh(PCy3)2Cl]2, [Rh(dmpe)Cl]2 (where dmpe= l,2-bis(dimethylphosphino)ethane), and [Rh(C8H14)Cl]2 show essentially no catalytic activity.166 Application of [Rh(PEt3)2Cl]2 to the reaction of aniline with styrene gives a mixture of hydroamination and oxidative amination products, the latter predominating.167 Other related rhodium-catalyzed amination reactions (oxidative amination) have been reported.168 169... 

Intermolecular hydroamination or hydroarylation reactions of norbornene and cyclo-hexadiene carried out with catalytic amounts of Brpnsted or Lewis acid in ionic liquids have been found to provide higher selectivity and yields than those performed in classical organic solvents. This effect was attributed to the increases of the acidity of the medium and stabilization of ionic intermediates through the formation of supramolec-ular aggregates with the ionic liquid.38... 

The Brpnsted acidic anilinium salt [PhNH3+][ B(C6F5)4] has been developed as a catalyst for the hydroamination and hydroarylation of alkenes, such as styrenes, nor-bomene, cyclic alkenes, and cyclohexadiene, with anilines. The weakly coordinating... 

The diastereoselective addition of aniline to norbornene was accomplished using a catalytic amount of iridium(I). As the intermediate azametallacyclobutane 2 could be isolated its stereochemistry was determined by X-ray analysis both iridium and nitrogen occupy the exo position41. However, the scope of the amination method, with respect to the nature of the amine and the structure of the alkene, was not determined. Conversely, the analogous rhodium(I)-cat-alyzed reactions of norbornene and aromatic amines gave mixtures of hydroamination and hydroarylation products106. 

Indeed, Cu can be used in combination with tungstophosphoric acid to realize solvent-free acid-catalyzed hydroarylation and hydroamination of alkynes to give the Markovnikov products with a variety of arylamines [211]. Furthermore, gold catalysts have been used extensively with acid additives for a variety of amine and protected amine substrates [120,212]. More recently, Bertrand [189] was able to illustrate the useful apphcation of his [(CAACjAulBlCgFj) complex for intermolecular alkyne hydroamination with both primary and secondary amines (Table 15.14). 

Compared to the hydroamination of alkynes, the protocols for more readily available olefins were rather limited. Ackermann presented a TiCU-catalyzed hydroamination reaction of norbornene using a variety of functionalized amines. Regioselective hydroarylation occurs as a competing reaction and the chemose-lectivity for hydroamination products ranges from poor to excellent [312]. This protocol can also be utilized in the hydroamination of vinylarenes with some electron-deficient amines [313] and the hydroamination of enyne compound. In the latter reaction, a subsequent rearrangement gives rise to a tetrahydroisoquinoline derivative (Scheme 14.134). 

Table 2.12 Effect of aniline substitution on hydroamination and hydroarylation product ratios...

Table 2.13 Hydroamination and hydroarylation reactions of vinyl arenes...

Table 2.14 Hydroamination and hydroarylation reactions of other unsaturated substrates...

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