SABRE Hyperpolarization of Exchangeable Protons in Methanol- d 4 through Dynamic Covalent Bonds.

Utilizing para -hydrogen ( p -H 2 )-induced hyperpolarization to increase the sensitivity of nuclear magnetic resonance, especially signal amplification by reversible exchange (SABRE), has been widely studied. Here, we achieved hyperpolarization of exchangeable protons in methanol- d 4 by introducing dynamic covalent bonds as reversible exchange following the SABRE process. To release the hyperpolarized CD 3 OH, the pyridine-based ligands with aldehyde groups underwent acetal exchange between the aldehyde and hydroxyl groups of CD 3 OH after being first hyperpolarized by SABRE. Our mechanistic study highlights the importance of the reversible exchange of functional groups and chemical kinetics in realizing hyperpolarization of exchangeable protons in methanol- d 4 . Our work broadens SABRE's chemical system compatibility and possible applications.