Fig. 1: Background of deuteration reactions.
From: Scalable reductive deuteration of (Hetero)Aryl chlorides with D2O

A Deuterated pharmaceutical compounds. B Proportion of aryl chlorides and prices of deuterium sources. C Nucleophilic deuteration with a strong base. D Hydrogen isotope exchange (HIE) reaction. E Deuteration by photo- electro- or mechano-chemistry. F Traditional transition-metal catalyzed deuteration. G Catalytic reductive deuteration of aryl chlorides with D2O.