Trifluoroacetamides , to protect amines

Protected primary allylic amines were generated from allylic carbonates and ammonia equivalents. Iridium-catalyzed allylic substitution has now been reported with sulfonamides [90, 91], imides [89, 91-93], and trifluoroacetamide [89] to form branched, protected, primary allylic amines (Table 5). When tested, yields and selectivities were highest from reactions catalyzed by complexes derived from L2. Reactions of potassium trifluoroacetamide and lithium di-tert-butyhminodi-carboxylate were conducted with catalysts derived from the simplified ligand L7. Reactions of nosylamide and trifluoroacetamide form singly-protected amine products. The other ammonia equivalents lead to the formation of doubly protected allylic amine products, but one protecting group can be removed selectively, except when the product is derived from phthalimide. 

Monoalkylation of support-bound amines can also be realized by a three-step protocol involving initial protection/activation of the amine (e.g. as 2-nitrobenzenesulfon-amide [132,133], trifluoroacetamide [102], or 4,4 -dimethoxybenzhydrylamine [66]) followed by N-alkylation and deprotection. In particular, if monomethylations (see, e.g., Entry 7, Table 10.7) or allylations are to be performed, this three-step strategy will generally give the best results. 

A simple modification of this technique has dramatic effects on the stability of the protecting group. If trifluoroacetyl is used rather than acetyl, the trifluoroacetamide (N-COCF3, N-TFA) is generated. Trifluoro-acetyl is usually attached by reaction of the amine with trifluoroacetic anhydride [(CF3C0)20] in the presence of triethylamine or pyridine, This group retains its stability to acid but is more sensitive to base (pH 1-... 

In contrast to esters, amide hydrolysis usually requires rather forcing conditions hence, amide protection of amines is not as common as gentler alternatives. Notable exceptions include trifluoroacetamides and phthalimides. Trifluoroacet-amides are so labile that they can be removed with potassium carbonate in methanol under conditions that preserve some methyl esters. 

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