Cleavage benzyl ethers

An 6>-nitrobenzyl ether.can be cleaved by photolysis. In tyrosine this avoids the use of acid-catalyzed cleavage and the attendant conversion to S-beirayltyrosine. (Note that this unwanted conversion can also be suppressed by the addition of thioanisole see section on benzyl ether cleavage.)... 

This is a fluorescent benzyl ether used for 2 -protection in nucleotide synthesis. It is introduced using 1 -pyrenylmethyl chloride (KOH, benzene, dioxane, reflux, 2 h, >65% yield). Most methods used for benzyl ether cleavage should be applicable to this ether. 

In secondary benzyl ethers, cleavage to the ketone usually predominates over the formation of alkyl benzoates (equation 328) [556]. 

Relative Rates for Substituted Benzyl Ether Cleavage... 

Photolysis at 365 nm in CH3CN improves the rate of DDQ promoted cleavage of benzyl ethers in that under these conditions cleavage occurs at rt. The MPM groups is still cleaved more rapidly and good selectivity can be achieved over benzyl ether cleavage. Unfortunately, olefins and acetylenes are incompatible with this protocol." ... 

For this purpose, nano dispersed palladium 15 was introduced into the composite material locating the Pd next to the polymer-bound ammonium cations. This was achieved after ionic attachment of Pd as palladate followed by reduction to Pd(0) and then pumping a solution of borohydride or hydrazine through the reactor (Scheme 12). Besides benzyl ether cleavage transfer hydrogenations were utilized for the reduction of aUcenes, aUcynes, and aromatic nitro groups (Scheme 13). 

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