Development of d 2-Benzylating Reagents Based on Pyridinium Salts

Abstract N-Benzyl Katritzky salts undergo highly efficient (>99%) H/D exchange at the benzylic C–H position upon treatment with D2O under basic conditions, giving d2-benzyl Katritzky salts bearing electron-neutral or electron-deficient aryl groups. Via iodination, these serve as electrophilic d2-benzylation reagents for various nucleophiles in high yield. Under photochemical conditions, they generate d2-benzyl radicals that add to heterocycles, olefins and alkynes. Reductive deamination provides selective access to d1-, d2-, and d3-methyl arenes, which are useful for deuterated drug synthesis.