Organogold(I) Phosphanes in Palladium‐Catalyzed Cross‐Coupling Reactions in Aqueous Media

Abstract

Cross‐coupling reaction of organogold(I) phosphanes with organic electrophiles in aqueous media has been investigated. Reactions between isolated aryl‐, alkenyl‐, or alkynylgold(I) phosphanes and aryl halides or triflates, alkenyl halides, and allyl acetates proceed under palladium catalysis conditions at room temperature or 80 °C in water with THF as a co‐solvent. The coupling reactions give good yields and are highly versatile and chemoselective, allowing the presence of free amino or hydroxy groups in the electrophile. This methodology was applied to the preparation of substituted phenylalanine esters in a demonstration that gold(I) organometallics are suitable reagents for metal‐catalyzed cross‐coupling reactions under protic conditions.

Reactivity of Polar Organometallic Compounds in Unconventional Reaction Media: Challenges and Opportunities

“…However, Sarandeses and co‐workers have recently expanded the scope of this transformation, by being the first to employ organogold(I)–phosphane derivatives (RAuPPh 3 ) as organometallic nucleophiles in water. Under these conditions, reactions between isolated aryl‐, alkenyl‐ or alkynylgold(I)–phosphanes and aryl halides or triflates were shown to proceed at room temperature (or at 80 °C) in water/THF mixtures 89. These Pd‐catalysed reactions delivered the corresponding coupling products in good yields and with high chemoselectivity, being compatible with free amino or hydroxy groups present in the electrophile.…”

Experimental and DFT Study of the [AuAr(AsPh3)]-Catalyzed cis/trans Isomerization of [PdAr2(AsPh3)2] (Ar = C6F5 or C6Cl2F3): Alternative Mechanisms and Its Switch upon Pt for Pd Substitution

“…In the last years, many examples of coupling reactions involving R-for-X Pd/Au transmetalations have been reported, in which organogold complexes participate as stoichiometric reagents, − or are used as cocatalyst. − The transmetalation reaction has been studied in some cases by computational methods, but quantitative experimental data are scarce. − In 2012, we reported a kinetic and computational study on the Rf/Cl exchange (transmetalation) between [PdRf 2 L 2 ] and [AuClL] (L = AsPh 3 ) . In that work, we proposed that [AuClL], acting as “incoming ligand”, substituted one L ligand at the palladium complex; at that step, the transition state displayed a Pd–Au interaction.…”

Gold and Palladium Mediated Bimetallic Catalysis: Mechanistic Investigation through the Isolation of the Organogold(I) Intermediates

“…Besides the fact that isolation of this organogold compound validates the proposed mechanisms, they also show interesting synthetic possibilities. For example, organogold­(I) compounds are useful precursors for cross-coupling reactions through transmetalation with palladium − or nickel . It is this transmetalation that is also important for bimetallic catalysis.…”