Protective for amides

Protection of the amide — NH is an area of protective group chemistiy that has received little attention, and as a consequence few methods exist for amide — NH protection. Most of the cases found in the literature do not represent protective groups in the true sense, in that the protective group is often incoiporated as a handle to introduce nitrogen into a molecule rather than installed to protect a nitrogen which at some later time is deblocked. For this reason many of the following examples deal primarily with removal rather than with both formation and cleavage. 

Reactivity Chart 9. Protection for the Amino Group Amides... 

Two new sections on the protection for indoles, imidazoles, and pyrroles, and protection for the amide — NH are included. They are separated from the regular amines because their chemical properties are sufficienth different to affect the chemistry of protection and deprotection. The Reactivity Charts in Chapter 8 are identical to those in the first edition. The chart number appears beside the name of each protective group when it is first discussed. 

The trityl group was introduced on a primary amide, RCONH2, in the presence of a secondary amide with TrOH, AC2O, H2SO4, AcOH, 60°, 75% yield. It is stable to BOC removal with 1 N HCl in 50% isopropyl alcohol, 30 min, 50°, but can be cleaved with TFA. The following table gives the cleavage rates with TFA for a number of protected primary amides. 

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