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Gold and palladium—a unique liason: A study of the transmetalation abilities of organogold compounds builds the basis for a new class of cross‐coupling reactions. Stable intermediates of gold catalysis deliver new complex products by a palladium‐catalyzed coupling reaction. (see Scheme)

An internal aryl-substituted ortho-alkyn-A C H T U N G T R E N N U N G ylphenol and a similar aniline with stoichiometric amounts of N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene-gold tosylate [(IPr)AuOTs] and tri-A C H T U N G T R E N N U N G ethylamine gave the aurated heterocycles as stable intermediates of the corresponding gold(I)-catalysed hydrooxylation and hydroamination reactions. X-ray crystal structure analyses of both products could be obtained. A similar internal alkyl-substituted ortho-alkynylphenol gave only the cycloisomerised product, no aurated intermediate could be detected.Keywords: alcohols; alkynes; amines; gold; hetarenes; mechanism Most reactions in the very active field of homogeneous gold catalysis [1] are based on the attack of a nucleophile Nu À H to either an allene-gold complex 1 or an alkyne-gold complex 2, both elementary reactions of central importance for gold catalysis. The activation of the carbon-carbon multiple bond by the gold complex is crucial, without this activation usually the nucleophilic addition is not observed. In both cases vinylgold species are formed; allenes deliver 3 with the nucleophile in an allylic position, alkynes lead to 4 with the nucleophile in a vinyl position (Scheme 1).For a long time, the vinylgold intermediates eluded detection and isolation, but in the last year three groups managed to isolate such species and unambiguously characterised them by X-ray crystal structure analyses. The first examples were provided by Hammond et al., who observed an only slow cyclisation of allenic esters with gold(I) catalysts and finally could show that in stoichiometric rather than catalytic reactions they can conveniently isolate stable vinylgold(I) phosphane complexes 5 (Figure 1), [2] the proto-deauration of 5 needs higher temperatures and strong acids. Next GagnØ et al. managed to isolate another allene-derived vinylgold(I) complex, by an intramolecular hydroarylation the phosphane complex 6 was obtained.[3] Then our group could show that with internal alkynes not only the regioselectivity of the ring closure of N-propargylic carboxamides would switch from a 5-exo-dig cyclisation to a 6-endo-dig cyclisation, also the vinylgold species could be detected when using phosphane ligands on gold and could even be isolated when using the gold(I) complex of the common NHC ligand N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr). [4] This was a quite general aproach, several representatives of the products 7 could be prepared in stoichiometric reactions in good yields and the spectroscopic properties as well the reactivity of this species could be investigated.

Gold und Palladium: eine einzigartige Liaison. Eine Studie der Transmetallierungsfähigkeit von Organogold‐Verbindungen bildet die Grundlage für eine neue Klasse von Kreuzkupplungen. Stabile Zwischenstufen der Gold‐Katalyse führen durch Palladium‐katalysierte Kupplungsreaktionen zu neuen, komplexen Produkten (Beispiel siehe Schema).

Different arylgold(i), one alkynylgold(i), and one vinylgold(i) triphenylphosphane complexes were subjected to electrophilic halogenation reagents. With N-chlorosuccinimid, N-bromosuccinimid, and N-iodosuccinimid as well as the Barluenga reagent, selectively halogenated compounds were obtained. Trifluoroacetic acid, as a source of protons, leads to a clean protodeauration. With N-fluorobenzenesulfonimide or Selectfluor, exclusively a homocoupling was observed. For the precursor of the vinylgold(i) complex, a similar oxidative coupling could be induced by gold(iii) chloride. Reactions with silicon or tin electrophiles failed.

Gold and Palladium Combined for Cross-Coupling. -Organogold(I) complexes undergo cross-coupling with aryl iodides (and bromides) in the presence of catalytic amounts of a palladium complex. The gold furanone complexes (I) exhibit an unprecedented thermal stability which allows reactions at elevated temperature. The gold can be recovered in nearly quantitative yield as iodo(triphenylphosphine)gold complex.-(HASHMI*, A. S. K.; LOTHSCHUETZ, C.; DOEPP, R.; RUDOLPH, M.; RAMAMURTHI, T. D.; ROMINGER, F.; Angew.

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