Hydroxymethylaniline Photocages for Carboxylic Acids and Alcohols




Skalamera, Dani
Bregovic, Vesna Blazek
Antol, Ivana
Bohne, Cornelia
Basaric, Nikola

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Journal of Organic Chemistry


ortho-, meta- and para-Hydroxymethylaniline methyl ethers 3–5-OMe and acetyl derivatives 3–5-OAc were investigated as potential photocages for alcohols and carboxylic acids, respectively. The measurements of photohydrolysis efficiency showed that the decaging from ortho- and meta-derivatives takes place efficiently in aqueous solution, but not for the para-derivatives. Contrary to previous reports, we show that the meta-derivatives are better photocages for alcohols, whereas ortho-derivatives are better protective groups for carboxylic acids. The observed differences were fully disclosed by mechanistic studies involving fluorescence measurements and laser flash photolysis (LFP). Photoheterolysis for the para-derivatives does not take place, whereas both meta- and ortho-derivatives undergo heterolysis and afford the corresponding carbocations 3-C and 4-C. The ortho-carbocation 4-o-C was detected by LFP in aqueous solution (λmax = 410 nm, τ ≈ 90 μs). Moreover, spectroscopic measurements for the meta-acetyl derivative 3-m-OAC indicated the formation of cation in the excited state. The application of an ortho-aniline derivative as a protective group was demonstrated by synthesizing several derivatives of carboxylic acids. In all cases, the photochemical deprotection was accomplished in high yields (>80%). This mechanistic study fully rationalized the photochemistry of aniline photocages which is important for the design of new photocages and has potential for synthetic, biological, and medicinal applications.



Alcohols, Solution chemistry, Reaction products, Fluorescence, Cations


Skalamera, D., Bregovic, V. B., Antol, I., Bohne, C., & Basaric, N. (2017). Hydroxymethylaniline Photocages for Carboxylic Acids and Alcohols. Journal of Organic Chemistry, 82(23), 12554-12568. https://doi.org/10.1021/acs.joc.7b02314.