Gadolinium triflate

Evans and Wu have prepared complexes derived from PyBOx ligands and samarium or gadolinium triflates that were efficient for the Diels-Alder reaction between various quinones and dienes [102] (see Scheme 38 for an example). 

Alleti, R., W.S. Oh, M. Perambuduru, Z. Afrasiabi, E. Sinn and V.P. Reddy, Gadolinium Triflate Immobilized in Imidazolium Based Ionic Liquids A Recyclable Catalyst and Green Solvent for Acetylation of Alcohols and Amines, Green Chemistry, 7, 203-206 (2005). 

The use of Ln(OTf)3 in the activation of aldehydes other than formaldehyde was also investigated [18]. The model reaction of 1-trimethylsiloxycyclohexene (2) with benzaldehyde under the influence of a catalytic amount of Yb(OTf)3 (10 mol%) was examined. The reaction proceeded smoothly in H20-THF (1 4), but the yields were low when water or THF was used alone. Among several Ln(OTf)3 screened, neodymium triflate (Nd(OTf)3), gadolinium triflate (Gd(OTf)3), Yb(OTf)3, and lutetium triflate (Lu(OTf)3) were quite effective, while the yield of the desired aldol adduct was lower in the presence of lanthanum triflate (La(OTf)3), praseodymium triflate (Pr(OTf)3) or thulium triflate (Tm(OTf)3) (Table 2). 

In 2009, Seidel and co-workers reported a Lewis acid-catalyzed [l,5]-hydride transfer reaction for the synthesis of polycyclic tetrahydroquinolines. It was found that the gadolinium triflate could efficiently accelerate the reaction (Scheme 4.4a). Preliminary attempts to realize asymmetric catalysis revealed that when a chiral magnesium bisoxazoline was utilized as the catalyst, the desired product 6a could be obtained in 74% yield and 30% ee, which was the first example of a catalytic asymmetric [l,5]-hydride transfer reaction by a chiral Lewis acid (Scheme 4.4b). The reason for the relatively low enanti-oselectivity was attributed to the reversibility of the ring-closure step in the presence of a strong Lewis acid catalyst. 

Pioneering work by Lubineau and coworkers showed that the aldol type reaction between a silyl enol ether and an aldehyde (the so-called Mukaiyama aldol reaction) occurred in water at room temperature with high syn stereoselectivity, albeit in low yields.However, the development of water-tolerant Lewis acids for this reaction has led to improved rates and chemical yields. Various lanthanides triflates, such as ytterbium triflate [Yb(OTf)3], scandium triflate [Sc(OTf)3], gadolinium triflate [Gd(OTf)3], or lutetium triflate [Lu(OTf)3], have been found to afford the aldol products between various aldehydes and silyl enol ethers in high yields in aqueous media, with good to moderate syn/anti diastereoselectivi-ties (Scheme 8.3, Table 8.1). ... 

Catalysis of the aminolysis of epoxides by lanthanide triflates (ytterbium, neodymium and gadolinium trifluoromethanesulphonate) has been reported (e.g. equation 26)68. 

The dinuclear Gd(III) complex has been obtained by treating the ligand with gadolinium oxide, Gd203, or with gadolinium hydroxide, freshly prepared from the chloride or triflate under basic conditions (pH adjusted to 8.5 with NaOH) in aqueous solution according to equation (2) ... 

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