This Account is dedicated to Dr. Yoshifumi Maki, Professor Emeritus at Gifu Pharmaceutical University, on the occasion of his 80th birthday. Deuterium-labeled compounds are widely utilized in various scientific fields. Although the H–D exchange reaction is a straightforward method to produce the deuterated organic compounds, it requires expensive deuterium (D₂) gas and/or harsh reaction conditions in conventional methods. This Account summarizes platinum-group metal on carbon (e.g., Pd/C, Pt/C, Ru/C, Rh/C)-catalyzed efficient multi and/or site-selective H–D exchange methods of various compounds including bioactive molecules, such as amino acids, nucleic acids, pharmaceuticals, agrochemicals, and sugars, under neutral and H₂-atmospheric conditions in D₂O. 1 Introduction and Background 1.1 H–D Exchange Reaction under Acidic or Basic Conditions 1.2 Transition-Metal-Catalyzed H–D Exchange Reaction 1.3 H–D Exchange Reaction under Supercritical State or Hydrothermal Conditions 1.4 Other H–D Exchange Methods 2 Pd/C-Catalyzed H₂–D₂ Exchange Reaction 3 Site-Selective Benzylic Deuteration under Normal Pressure at Room Temperature 4 Multi H–D Exchange Reaction under Heat Conditions 4.1 Multi H–D Exchange Reaction of Alkyl-Substituted Aromatics 4.2 Multi H–D Exchange Reaction of Heterocyclic Compounds 4.3 Multi H–D Exchange Reaction of Aromatic Nuclei 4.4 Multi H–D Exchange Reaction Using a Mixture of Pd/C and Pt/C or Pd–Pt Hybrid Catalyst 5 H–D Exchange Reaction of Simple Alkanes 6 H–D Exchange Reaction of Alcohols 6.1 The Regioselective H–D Exchange at the α-Position of Aliphatic Alcohols 6.2 The Regio- and Stereoselective Deuterium Labeling of Sugars 7 Conclusion

We have developed a mild and efficient protocol for the ligand-free and heterogeneous Pd/C-catalyzed hetero Suzuki–Miyaura coupling reaction that allows for the synthesis of both heteroaryl–aryl and heteroaryl–heteroaryl derivatives in good to excellent yields.