|Carbon dioxide - Silver benzoate "puts a ring on it"|
Source: Yamada, et.al. ACIEE, 2012
Makes me wonder: Did I somehow miss the signs? How long has this reagent been flying under my radar?
|In 1957, the Lone Ranger |
ruled the Silver Screen
In its heyday, the Prévost helped synthesize steroids, alkaloids, and polymers, and found its way into the hands of a Who's Who of the O-Chem 'golden age': Woodward, Fieser, Carothers, Winstein, Streitweiser, Gilman, Djerassi, Fries, Benkeser, Sondheimer, van Tamelen, and Witkop. Perhaps you're more of a mechanisms person? Check out this sweet 18O labeling work, courtesy of a young University of Washington chemist named Ken Wiberg (1957).
What about silver benzoate makes it so darn useful for these oxidations? First, you have a d10 late metal species, which loves to coordinate to π-bonds (alkenes, alkynes, allenes). Second, the softer nature of the resonance-stabilized benzoate might switch on different catalytic pathways, say, changing from inner- to outer-sphere. Finally, to the benzoate itself: our buddy Ken showed that it adds twice, producing a transient 5-membered, cyclic species that ultimately permits the second benzoate addition.