Hydroxide Ion‐Initiated Deuteration of Very Weak CH Acidsunder Phase Transfer Catalysis Conditions

The deuteration of organic compounds with pK_a values of up to ca. 34 has been achieved by a special type of phase transfer catalysis. As is well known, hydroxide ions can be extracted into an organic phase from aqueous sodium hydroxide in the presence of quaternary ammonium salts. It has now been shown that these extracted hydroxide ions are more basic than the hydroxide ions at the interface. Exploiting this observation, diphenylmethane, 10,11‐dihydrodibenzo[a,d]cycloheptene and xanthene (pK_a = 34, 31, and 27, respectively) could be deuterated quantitatively.