P-Halobenzyl ethers

An example of 3-fold relay deprotection in the second class depends on the selective conversion of a fairly inert p-halobenzyl ether to an activated p-ami-nobenzyl derivative by palladium (0)-catalysed animation.4 The subsequent deprotection is then achieved with Lewis or protic acids. Scheme 1.28 illustrates... 

Iterative deprotection of p-halobenzyl ether protecting groups... 

Another substituted benzyl ether in occasional use is the /7-chlorobenzyl ether, mainly because of the high crystallinity and added stability of these derivatives. Recently, a methodology to remove p-chloro- and bromobenzyl ethers in the presence of both benzyl and /7-methoxybenzyl groups was reported [15]. It employed a two-stage deprotection scheme where thep-halobenzyl group was first converted to an arylamine by Pd-catalyzed amination. The arylamine was then selectively cleaved under very mild acidic conditions. 

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