Protecting Groups Cleaved by Reductive Elimination

9 Protecting Groups Cleaved by Dissolving Metal Reduction 11 

11 Protecting Groups Cleaved by Transition Metal Catalysis 12 

An asterisk in the text Indicates that a pertinent review can be found at the end of the chapter. 

Protection is not a principle, hut an expedient Benjamin Disraeli, 17 March, 1845 

There are 7 tactical considerations which define how effectively a protecting group will best fulfil its assigned strategic role of shielding a functional group from destruction (or reaction with another functional group)  

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Many carbamates have been used as protective groups. They are arranged in this chapter in order of increasing complexity of stmcture. The most useful compounds do not necessarily have the simplest stmctures, but are /-butyl (BOC), readily cleaved by acidic hydrolysis benzyl (Cbz or Z), cleaved by catalytic hy-drogenolysis 2,4-dichlorobenzyl, stable to the acid-catalyzed hydrolysis of benzyl and /-butyl carbamates 2-(biphenylyl)isopropyl, cleaved more easily than /-butyl carbamate by dilute acetic acid 9-fluorenylmethyl, cleaved by /3-elimination with base isonicotinyl, cleaved by reduction with zinc in acetic acid 1-adamantyl, readily cleaved by trifluoroacetic acid and ally], readily cleaved by Pd-catalyzed isomerisation. 

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