Deoxygenative Deuteration of Carboxylic Acids with D 2 O

Abstract We report a general, practical, and scalable means of preparing deuterated aldehydes from aromatic and aliphatic carboxylic acids with D 2 O as an inexpensive deuterium source. The use of Ph 3 P as an O‐atom transfer reagent can facilitate the deoxygenation of aromatic acids, while Ph 2 POEt is a better O‐atom transfer reagent for aliphatic acids. The highly precise deoxygenation of complex carboxylic acids makes this protocol promising for late‐stage deoxygenative deuteration of natural product derivatives and pharmaceutical compounds.