Photolytic cleavage ester

NO BF )" have also been used to cleave amides. Since only tertiary amides are cleaved by potassium r-butoxide (eq. 6), this method can be used to effect selective cleavage of tertiary amides in the presence of primary or secondary amides. " (Esters, however, are cleaved by similar conditions.) Photolytic cleavage of nitro amides (eq. 7) is discussed in a review. ... 

Phenacyl esters of benzoic acid, of amino acid derivatives, and of gib-berillin A3 undergo photolytic cleavage at >313 nm, giving, in each case, the free carboxylic acid and the corresponding acetophenone (see Scheme 29) 84,85 -pijg yjeijs Qf free carboxylic acids (33-96%) vary considerably,... 

Most photocleavable linkers for carboxylic acids used today are based on the photoisomerization of 2-nitrobenzyl esters and on the light-induced cleavage of phen-acyl esters (Figure 3.10). Several possible mechanisms have been proposed for the photolytic cleavage of benzoin esters. One of the most recent is the dissociation of the excited phenacyl ester into a carboxylate and a phenacyl cation ( photosolvolysis , Figure 3.10 [136]). 

Table 3.6. Photolytic cleavage of resin-bound esters.

Examples of the cleavage of support-bound carbonates are given in Table 3.36. Depending on the structure of the carbonate, acidolytic, base-induced, nucleophilic, or photolytic cleavage can be used to release the alcohol. Acidolysis of the benzylic C-O bond of resin-bound benzyl carbonates leads to the release of an unstable carbonic acid ester, which undergoes decarboxylation to yield the alcohol. 

Scheme 16.9. Modification and photolytic cleavage of a phenacyl ester-based linker.

Two general routes to formyl-esters using ring cleavage reactions have been described one employs an electrolysis of lactams whereas a second involves a photolytic cleavage of cyclic /3-keto-esters to give w-formyl-a,/3-unsaturated esters. ... 

SCHEME 8 Reaction pathways for photolytic cleavage of MCM esters. 

Photolytic. Photolysis of permethrin in aqueous solutions containing various solvents (acetone, hexane, and methanol) under UV light (1 >290 nm) or on soil in natural sunlight initially resulted in the isomerization of the cyclopropane moiety and ester cleavage. Photolysis products identified were 3-phenoxybenzyldimethyl acrylate, 3-phenoxybenzaldehyde, 3-phenoxybenzoic acid, mono-chlorovinyl acids, cis- and fra/is-dichlorovinyl acids, benzoic acid, 3-hydroxybenzoic acid, 3-hydroxybenzyl alcohol, benzyl alcohol, benzaldehyde, 3-hydroxybenzaldehyde, and 3-hydroxybenzoic acid (Holmstead et ah, 1978). 

Sultones undergo photolytic ring cleavage and the intermediate sulfenes are trapped by methanol to form esters , viz. 

The photolytic pathway for A -l,3,4-oxadiazolines (22) (Scheme 8) begins with C-N cleavage to form diradicals (23), followed by ester elimination and generation of diazoalkanes (24). Further photolysis gives the corresponding carbenes. In a study of (22b) and (22c), flash-photolysis and two-wavelength continuous... 

The photolytically induced cleavage of the BHQ ester has a greater quantum efficiency than does the 4,5-dimethoxy-4-nitrobenzyl (DMNB) ester and the 6-bromo-7-hydroxycourmarin-4ylmethyl (Bhc) ester. It can be used in vivo because it has sufficient sensitivity to multiphoton-induced photolysis. It is also more soluble than the DMNB and the Bhc esters, which is advantageous for in vivo applications. ... 

The hydrolysis of OPs to less harmfiil compounds is an important aspect for environmental decontamination. The phosphate ester bond is prone to cleavage this occurs mostly by hydrolysis but photolytic degradation by sunlight is also possible [49]. Biological pathways for decontamination such as bioremediation have attracted recent attention [9]. In the context of this thesis the term bioremediation is used when plants, microorganisms or enzymes derived from them are used to uptake or break down environmental contaminants e.g. heavy metals, chemicals from oil spills or pesticides [43, 50-52]. 

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