Site-Selective Benzylic C–H Hydroxylation in Electron-Deficient Azaheterocycles

20 February 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Benzylic C–H bonds can be converted into numerous functional groups, often by mechanisms that involve hydrogen atom transfer at the key bond breaking step. The abstracting species is most often an electrophilic radical, which makes these reactions best suited to electron-rich C–H bonds to achieve appropriate polarity matching. Thus, electron deficient systems such as pyridine and pyrimidine are relatively unreactive, and relatively underrpresented in substrate scopes. In this report, we describe a new method for benzylic hydroxylation—essentially an unknown reaction in the case of pyrimidines—that makes use of an iodine(III) reagent to affords very high selectivity towards electron-deficient azaheterocycles in substrates with more than one reactive position and prevents over-oxidation to carbonyl products. The identification of key reaction byproducts supports a mechanism that involves radical coupling in the bond forming step.


C-H functionalization

Supplementary materials

Supporting Information
General procedures; Synthesis of Starting Materials; Development of Reaction System; C-H Hydroxylation of Azaheterocycles; Reactions in Support of Radical Mechanism; Details of SciFinder(R) Searches; References.


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