Epoxidation amidine-catalysed

Gd(OTf)3 is prepared by the general method described above. If suspect, then add aqueous triflic acid (50% vA) and proceed as above. It catalyses the aminolysis of epoxides in an extraordinarily efficient manner in aprotic solvents (e.g. toluene, CH2CI2) with complete trans stereoselectivity and high regioselectivity [Chini et al. Tetrahedron Lett 35 433 1994]. It also catalyses the reactions between nitriles and amines to yield a variety of amidines which, depending on the amine, can be used to prepare cyclic amidines, pyrimidines and x-triazines [Forsberg et al. J Org Chem 52 1017 79S7]. It is a water-tolerant Lewis acid used in aldol reactions of silyl enol-ethers and aldehydes in -79-89% yields (see below) [Kobayashi Hachiya J Org Chem 59 3590 1994]. 

A detailed kinetic study using UV-vis, FTIR (Fourier-transform infrared), and NMR spectroscopy a Hammett plot with /0 = -h1.98 using para-substituted styrene oxides an inverse solvent kinetic isotope effect (KIE) (fcnHp/ HHP-d2) = 0.86 and nonlinear effects studies" have all shown that the (salen)Co- (J) and amidine-co-catalysed enantioselective ring opening of terminal- and mew-epoxides by fluoride ion (forming trans- -ttuoTO alcohols in a 42-89% yield with 84-99% ee) occurs by the mechanism shown in Scheme 5. /-BuOOH oxidizes the Co(H) to Co(III) in the (salen)Co(III) catalyst. PhCOF provides the fluorine for the reaction. 

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