Fig. 4. Scope of the decarboxylative deuteration. ^aStandard conditions A: aliphatic acids 1 (0.2 mmol), PC-I (2 mol%), 2a (10 mol%), 2,4,6-collidine (1.0 equiv.), DCM/D₂O (4 : 1, v/v, 2 mL), blue LEDs, 10–20 h. ^bStandard conditions B: cesium carboxylate (0.2 mmol), PC-III (1 mol%), 2a (10 mol%), DCM/D₂O (4 : 1, v/v, 2 mL, 110 eq. of D₂O), 45 W blue LEDs, 10–20 h. ^cThese products are readily volatile and yields are determined by GC. Isolated yields are shown and the deuterium incorporation ratio was determined by ¹H NMR spectroscopy (<95% D) or HRMS (>95% D).