Silver hydroamination with

Hexa luoro-2-butyne, vinylacetylene, and 1,3-butadiyne can be hydroaminated without catalyst [265-267]. However, the reaction of 1,3-butadiyne with Et2NH is accelerated and gives a better yield in the presence of silver or silver diacetylide (29% vs. 19% without catalyst) (Eq. 4.67) [268]. 

A novel one-pot domino process was developed to synthesize substituted 1,2-dihydroquinoline derivatives 102 with high regioselectivity using a silver catalyst <05OL2675>. Scheme 29 shows the proposed pathway, which starts with the hydroamination of alkyne 103 and aniline 104. This is followed by C-H addition with another alkyne 103 and C-H addition cyclization to give intermediate 105. The final step is another C-H addition with alkyne 103 yielding the desired product 102. The scope and mechanism of this one-pot process is still under investigation. 

The corresponding intermolecular addition of cyclic ureas to terminal alkenes is catalyzed by Au[P(/-Bu)2(o-biphenyl)]Cl and AgOTf, and it provided alkylated ureas in high yield at 100 °C. The reaction even works with ethylene and other gaseous olefins. In the presence of chiral gold(I) pre-catalyst [Au2 (S)-3,5-r-Bu-4-MeO-MeOBIPHEP Cl2] and silver triflate, the hydroamination products were obtained with 71-76% ee (Scheme 4-68). Treatment of cyclic ureas with allylic alcohols in the presence of cationic gold(I) catalysts afforded allylated ureas with... 

While effective bimetallic catalyst design has the potential to lead to an enhancement of the reaction rate, the use of chiral bimetallic catalysts has also been explored to enhance the enantioselectivity of a reaction. Such bimetallic chiral induction is excellently demonstrated by the use of digold catalysts for the hydroamination of prochiral substrates such as allenes and alkenes [59]. The bimetallic Au catalyst 66, for example, was shown to be an effective catalyst for the hydroamination of amino-allenes in the presence of a silver salt activator (Scheme 24) [106]. The highest enantioselective induction for this reaction was achieved with a 1 1 ratio of AgBp4 to 66 (51 % ee) suggesting that the monocationic... 

Silver(I) salts are often utilized as catalysts for addition reactions. Kozmin and Sun have recently shown that AgNTf2 is a catalyst of choice for the hydroamination of siloxy alkynes with either secondary amides or carbamates to give silyl ketene am-inals [34]. The addition occurs in a syn selective manner, for instance, the reaction of siloxy alkyne (24) with carbamate (25) produces silyl ketene aminal (26) in 86% yield at room temperature under the influence of 1 mol% of AgNTf2 (Scheme 18.9). A six-membered chelated transition state is proposed to explain the high syn selectivity. Diastereoselective bromohydroxylation and bromomethoxylation reactions of cinnamoyl compounds possessing a chiral auxiliary are also effectively promoted by silver(I) salts such as AgNOs [35]. The asymmetric halohydrin reaction has been successfully applied into stereoselective syntheses of (-)-chloramphenicol and (+)-thiamphenicol. Csp-H iodination [36], hydrosilylation of aldehydes [37], and deprotection of TMS-alkynes [38] are also catalyzed by silver (I) salts. 

Intramolecular nitrogen attack in propargylated enaminones allows silver-catalyzed access to functionalized pyrroles. This Ag-promoted hydroamination can also be used to obtain A bridgehead pyrroles. Silver nitrate-mediated cyclization of allenylamines, available from Uthiated alkoxy allenes and imines or through reaction of l-(lV-carbamoyl)-alkylcuprates with propargyl substrates, provides access to 2,5-dihydropyrrole derivatives. Iminoallenes can be used for the synthesis of substituted p)moles in moderate yields in the presence of potassium carbonate. ... 

Both copper- and silver-catalyzed three-component reactions between an aldehyde, terminal alkyne, and secondary amine have been used to generate propargylamines [17, 18] The copper-catalyzed hydroamination between hydroxylamine esters and unactivated aUcenes generates amines with the desired regiochemistry for a wide range of diverse substrates [20]... 

An example of a cascade reaction combining enamine and silver catalysis for synthesis of 1,2-dihydroisoquinoline derivatives is shown in Fig. 8.26. In the first step, nucleophilic enamine formed from the ketone and proline reacts with the imine, which is generated from the aldehyde and the amine. As a result, the Mannich base is formed, which then undergoes a hydroamination reaction in the presence of silver catalyst. 

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