A new article published in Molecules described a simple and general procedure to accomplish selective photochemical reaction sequences for two chromophores that are responsive to similar light frequencies.

This method was based on the exploitation of differences in the molar absorptivity at certain wavelengths of photosensitive groups, which is enhanced by utilizing light-absorbing auxiliary filter molecules or "sunscreens". Thus, the filter molecule hinders the reaction pathway of the least absorbing molecule or group, allowing for the selective reaction of the other. The method was applied to various photochemical reactions, from photolabile protecting group removal to catalytic photoinduced olefin metathesis in different wavelengths and using different sunscreen molecules.

These sunscreens were shown to be effective also when applied externally to the reaction mixture, avoiding any potential chemical interactions between sunscreen and substrates and circumventing the need to remove the light-filtering molecules from the reaction mixture. The authors reported that this method was simple and could be generally applied.

Source: Molecules. 2020 May 1;25(9):E2125. doi: 10.3390/molecules25092125.