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Two new cationic dinuclear gold(I) complexes, [Au2{μ(P,N)-5}2]X2--in which X=NTf2 (7; Tf=trifluoromethanesulfonate) or SbF6 (8) and 2-(diphenylphosphanyl)benzonitrile (5) is a P,N-bridging donor--have been synthesized and structurally characterized. These air-stable species and their dimeric and polymeric analogues possessing 1'-(diphenylphosphanyl)-1-cyanoferrocene (1) as the bridging ligand, [Au2{μ(P,N)-1}2](NTf2)2 and [Au{μ(P,N)-1}]n[SbF6]n, were used as precatalysts in various Au-mediated C-C and C-O bond-forming reactions. The reactivity of these complexes revealed the hemilabile nature of their P,N ligands. In the series of tested precatalysts, complex 8 exerted particularly high catalytic activity at low Au loading, even in reactions that usually require high amounts of gold catalyst to proceed efficiently under standard reaction conditions. [ABSTRACT FROM AUTHOR]

An efficient synthesis of polysubstituted 2-alkenylfurans using Ca(NTf2)2/KPF6 as a catalytic mixture is described. It is based on the cycloelimination of readily available propargyl alcohols tethered to β-keto esters under dry conditions to avoid competitive Meyer-Schuster rearrangement. The furan can be further functionalized in situ by a calcium-catalyzed Friedel-Crafts-type reaction with secondary and tertiary alcohols. The title reaction allows for the high-yielding preparation of di-, tri-, and tetrasubstituted 2-alkenylfurans, which are important subunits of bioactive compounds. [ABSTRACT FROM AUTHOR]

The intramolecular condensation of -keto esters to give propargyl alcohols is described. The substrates have two electrophilic sites and two nucleophilic sites. The site selectivity can be fully controlled. In the presence of a calcium-based catalyst and under anhydrous conditions, O-addition products are isolated. On the other hand, traces of water or iPrOH as additive encourage calcium-catalyzed Meyer-Schuster rearrangements. The resulting enones may be further transformed into endo- Michael addition products. The regioselectivity of the attack of the enolate can be changed by using 1-[3,5-bis(trifluoromethyl) phenyl]-3-[2-(dimethylamino)cyclohexyl]thiourea (TUC) as organocatalyst, which promotes the formation of aldol-condensation products of high synthetic interest. DFT calculations rationalize the preference for the aldol condensation when TUC is used instead of the endo-Michael addition. [ABSTRACT FROM AUTHOR]

We report a rare case of alkene transfer hydrogenation using a main-group compound instead of a transition-metal complex as catalyst. We disclosed that 1,4-cyclohexadiene can be used as H2 surrogate towards olefin reduction in the presence of [IPrGaCl2][SbF6]. Hydrogenative cyclizations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst. [ABSTRACT FROM AUTHOR]