Enol ethers, aminolysis

Uracil and thymine derivatives are obtained from cyanoacetic acid and A -alkylurethanes. An amide 16 is formed first, which condenses with orthoformic ester to give the enol ether 17 aminolysis of 17 leads to 18 which on cyclization yields 5-cyanouracil 19 Shaw synthesis) ... 

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]. 

---