Aminolysis of Epoxides

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

Overman and Flippin utilized diethylaluminum amides for facile aminolysis of epoxides [71], The procedure involved treating a primary or secondary amine in CH2CI2 with EtsAl (1 equiv.) at room temperature for 30 min, then reaction with epoxide (1 equiv.) overnight. Hydrolysis of the resulting amino aluminate eventually afforded the /8-amino alcohol product in good yield. Aminolysis of cyclopentene oxide with diethylaluminum anilide is shown in Sch. 43 as a typical example. 

The trend of accelerating reactions by using more polar solvents was demonstrated for the aminolysis of epoxide 14 with (-BuNH2 (Figure 4.10). Faster reactions were noted as the solvent was changed from benzene to (PrOH to MeOH to HzO [32]. As shown in Figure 4.10b, the use of more polar solvents greatly improved the yield from amination [33]. Each of these reactions probably involves a polar intermediate or transition state that is stabilized by solvent interaction. 

Aminolysis of epoxides is also promoted by high pressure or silica gel catalysis. For example, 2V-(p-hydroxyalkyl)glycine esters have been prepared in high yields by nucleophilic substitution at 1.0 GPa or under silica gel catalysed conditions of various epoxides with a stoichiometric amount of tert- butyl glycinate. 

Aminolysis of epoxides. The reaction of epoxides with glycine /-butyl ester is catalyzed by silica gel and promoted by high pressure. 

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]. 

Alumina prepared by conventional hydrolysis of aluminum compound precursors is covered by surface hydroxyl groups. High-temperature calcination is needed in order to expose the surface coordination unsaturation of A1 ions. A new method, which involves stoichiometric hydrolysis of an amine-Al alkoxide monomeric complex, can generate alumina with a surface that is covered with far fewer hydroxyls without high-temperature postsynthesis treatment. In this method, the coordination unsaturation site of A1 is protected with an amine throughout the preparation process. The bound amine on the alumina surface can be exchanged with other bases, and the final solid is a Lewis-acid catalyst and catalyzes reactions such as aminolysis of epoxide. The chemistry in the preparation of such an alumina is described. 

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