Gold -catalyzed transformations

Representative procedure for the gold-catalyzed transformation ofhomopropargyl ethers to heterocyclic ketones. l-((2R,6S)-6-((R)-2-Hydroxypentyl)-l-(2-nitrophenylsulfor l)-piperidin-2-yl)propan-2-on ... 

The cycloisomerization of a- or (3-hydroxyallenes can also be carried out in water, for example with tetrachloroauric acid as catalyst. This system was used for the first example of a tandem lipase/gold-catalyzed transformation. The one-pot kinetic resolution/cycloisomerization of racemic allenic acetates with Burkholderia cepacia lipase (PS Amano SD Amano Enzyme USA Co., Ltd., Elgin, IL) and HAuCU afforded 2,5-dihydrofurans as well as unreacted starting material with 28-50% isolated yield and 86-98% ee (Scheme 4-96). The mutual tolerance of the Lewis-acidic gold catalyst with the Ixwis-basic lipase is maintained as long as low amounts of the former are used. 

Enantioselective Gold Catalyzed Transformations Based on Chiral,... 

ORGANOGOLD CATALYSIS HOMOGENEOUS GOLD-CATALYZED TRANSFORMATIONS FOR A GOLDEN JUBILEE... 

While sulfur derivatives are generally considered as being poisonous for gold, they have nevertheless been successfully used in several gold-catalyzed transformations (Scheme 16.15) [19]. Their number remain however very limited when compared to reactions involving oxygen or nitrogen nucleophiles. 

In gold catalyzed transformations, the carbenoid intermediates such as 31 arising from a 5-exo-dig cyclization can also be either oxidized in the presence of Ph2SO leading to carbaldehyde 32 or trapped by an alkene to give bis-cyclopropanic derivatives 33 (Scheme 5.12) [55-57]. 

Chiral bisphosphine gold(I) complexes have been employed in the asymmetric variants of a number of gold-catalyzed transformations. Michelet and coworkers reported... 

Recently, Wetzel and Gagosz [49] reported gold-catalyzed transformations of o-azidoarylalkynes. As shown in Scheme 4.29, the azido group can act as a... 

SCHEME 4.29 Gold-catalyzed transformation of o-azido arylalkynes. 

---