Desulfonylation of Tosyl Amides through Catalytic Photoredox Cleavage of N-S Bond Under Visible-Light Irradiation

摘要

Sulfonamides are robust protecting groups that are easy to purify and are very stable under various reaction conditions. However, one of their major limitations is that they require rigorous deprotection conditions. Most desulfonylation methods usually require harsh acidic or reductive reaction conditions; this further limits their efficacy with substrates that bear sensitive functional groups. Several desulfonylation methods have been successfully established for molecules that contain sensitive functional groups; these methods involve the use of electrolysis, Bu_3SnH/2,2'-azobis (2-methylpropionitrile) (AIBN), tetrabutylammonium fluoride (TBAF), SmI_2, Mg in MeOH, iodotrimethylsilane, alkali metals on silica, phase-transfer catalysis, low-valent titanium reagents, and photoinduced desulfonylation. Although these methods have provided more options for the synthetic community, challenges still remain. For instance, some of these methods require the use of toxic or moisture sensitive reagents, while others often result in the formation of byproducts that are difficult to remove. As a result, the development of a novel, mild and efficient desulfonylation method, with high functional group tolerance, is highly desirable.