Protection for the Amide NH

Although a methyl group is usually not considered as a protective group, it is easily introduced with NaH and Mel in THF and amazingly can be cleaved via a free radical process.  

The allyl group was used to protect the nitrogen in a P-lactam synthesis, hut was removed in a four-step sequence.  

Methods that give the enamide are included, since these can be cleaved by ozonoly-sis and in principle by acid-catalyzed hydrolysis. 

Rh(Ph3P)3Cl, toluene, reflux, 81% to the enamide O3, MeOH DMS NaHCOs, 87% yield.  

Cleavage of the enamide by the Johnson-Lemieux reaction. The allyl group was the only successfully cleaved group among the many that were examined. 

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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. 

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