Gold(I)-triflimide (AuNTf 2 )complexes of H-KITPHOS and o-MeO-KITPHOS have been prepared and shown to be efficient catalysts for a range of intramolecular cyclisations to afford phenols, acylindenes, alkylidene oxazoles, tetrahydropyrans and lactones, in the majority of cases these catalysts are superior to those previously reported.

In the present study we describe the efficient synthesis of various Au(I) complexes supported by NHC ligands. Some of these ligands have a pendant pyridine arm that is linked with various tethers (CH 2 ) n to the NHC backbone (n = 0-2). The chloride in the Au(I) complexes is easily and cleanly replaced by an aryl group upon reaction with an aryl-Grignard reagent. The thus obtained aryl Au(I) complexes are cleanly oxidized to the corresponding Au(III) complexes with phenyliodoso dichloride, as are the corresponding halide Au(I) complexes. The attempted salt metathesis with the parent Au(III) complex led to the oxidative coupling of the aryl residues with formation of the Au(I) complex. Some of the complexes are promising catalysts in the cycloisomerization of an ω-alkynylfuran to isobenzofuranol in the presence of a silver salt. For those precursors with pendant pyridine arms, a cationic dimeric Au complex was isolated and characterized, which represents a catalyst resting state and forms under reaction conditions.

New tetrathia[7]helicene-based (7-TH-based) gold(I) complexes 6 and 7 have been readily prepared by reaction of the respective phosphine ligands 2 and 3 with Au(tht)Cl in a 1:1 and 1:2 molar ratio, respectively. These complexes have been fully characterized by analytical and spectroscopic techniques as well as quantum chemical calculations. The molecular structure of dinuclear complex 7 has been determined by single-crystal X-ray diffraction, showing a gold-gold interaction of 3.1825(3) Å and a significant contraction of the 7-TH total dihedral angle. Au(I) complex 7 displays luminescence emission at room and low temperature in diluted solution and in the solid state. Quantum chemical calculations show that the luminescence emission at room temperature is primarily due to slightly perturbed fluorescence emission from purely ππ* excited states of the conjugated helicene scaffold. At 77 K phosphorescence emission is displayed as well. Preliminary studies on the use of 6 and 7 as catalysts in typical Au(I)-catalyzed cycloisomerizations have demonstrated the reactivity of these systems in the intramolecular allene hydroarylations and the hydroxycarboxylation of allene-carboxylates.

A gold-catalyzed phenol synthesis was successfully used in the synthesis of dihydroisocoumarins for the first time. A large number of gold(i) complexes were prepared and tested; only complexes based on the biarylphosphine motif were successful.

Electrophilic gold(I) triflimide (trifluoromethanesulfonimide) complexes of electron-rich ortho,ortho'-disubstituted KITPHOS (11-dicyclohexylA C H T U N G T R E N N U N G phosphino-12-phenyl-9,10-ethenoanthracene) monophosA C H T U N G T R E N N U N G phines are efficient catalysts for intramolecular cycloisomerizations that afford phenols, 3-acylindenes and methylene-oxazolines; comparative catalyst testing showed that these catalysts either competed with or outperformed that based on SPHOS [2-(2',6'-dimethoxybiphenyl)dicyclohexylphosphine]. An electron-rich biarylmonophosphine containing a single ortho-methoxy substituent, prepared by rhodium-catalyzed [2 + 2 + 2] cycloaddition between a 1-alkA C H T U N G T R E N N U N G ynyl(dicyclohexylphosphine) oxide and 1,7-octadiyne, also formed a highly efficient catalyst for the same transformations. Monitoring of comparative catalyst testing between a KITPHOSbased gold(I) triflimide complex containing a coordinated tetrahydrothiophene and its counterpart coordinated solely by the triflimide anion revealed that the former is an order of magnitude less efficient than the latter, confirming that tetrahydrothiophene can be an effective catalyst inhibitor.

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Ring closure reactions O 0130Gold (I) Complexes of KITPHOS Monophosphines: Efficient Cycloisomerization Catalysts -[all yields determined by NMR]. -(HASHMI*, A. S. K.; LOOS, A.; LITTMANN, A.; BRAUN, I.; KNIGHT, J.; DOHERTY, S.; ROMINGER, F.; Adv.