Deoxygenative Deuteration of Carboxylic Acids with D2 O.

We report a general, practical, and scalable means of preparing deuterated aldehydes from aromatic and aliphatic carboxylic acids with D2 O as an inexpensive deuterium source. The use of Ph3 P as an O-atom transfer reagent can facilitate the deoxygenation of aromatic acids, while Ph2 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.