Silver bromide photolysis

Gurney RW, Mott NF (1938) The theory of the photolysis of silver bromide and the photographic latent image. Proc Roy Soc (A) 164 151-167... 

The imidazole on the histidine side chain may be protected as a 2-nitrobenzyl derivative which leads to a nnixture of N"- and N -derivatives. Generally, the x-derivative dominates, and can often be isolated pure by recrystaUization. The group is installed by reaction of the silver salt of Boc-His-OMe (13) with 2-nitrobenzyl bromide in refluxing benzene (Scheme 20).b l The product 14 was immediately saponified and, after acidification, extracted into ethyl acetate to give the acid in yield 60-70%. Photolysis of this material was affected by irradiating a 0.001 M solution in dioxane for 1 hour with Pyrex-filtered UV light from a mercury vapor lamp to give Boc-His-OH in quantitative yield. 

Vinyl cations, generated from 3-arylvinyl bromides by silver(I)-assisted solvolysis or by photolysis, are trapped by nitriles to yield isoquinolines (equation 24). ... 

The sulfonate is prepared from the silver salt of the sulfonic acid by reaction with the phenacyl bromide in CH3CN at reflux for 48 h (35-39% yield). It is cleaved by photolysis at >280nm in benzene (90-94% yield). The corresponding phosphate ester is cleaved similarly. 

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