The stable radical TEMPO is an an important molecule for organic catalysis, and its protonated cousin TEMPO-H is an excellent chemical source of hydrogen. However, Jason Masuda and Jason Clyburne (Saint Mary’s University, Canada) were concerned that, due to the current synthetic route, water present in TEMPO-H could lead to unwanted side reactions.
In this HOT paper they overcome this problem by reporting the first anhydrous route to TEMPO-H (2,2,6,6-tetramethylpiperidin-1-ol), by treating the sodium salt of TEMPO with triethylamine hydrochloride. They show that the anhydrous form is not only more stable during synthesis, but that it has a different structure and reactivity patterns as well. They tested their anhydrous compound against several molecules with low valence carbon centres such as carbenes and ketenes, demonstrating the use of the anhydrous form in avoiding side reactions and creating different complex structures.
- Preparation of anhydrous TEMPO-H
You can read the full details of the synthesis and characterisation for free until 14th May:
Anhydrous TEMPO-H: reactions of a good hydrogen atom donor with low-valent carbon centres
Nick A. Giffin, Miller Makramalla, Arthur D. Hendsbee, Katherine N. Robertson, Cody Sherren, Cory C. Pye, Jason D. Masuda and Jason A. C. Clyburne
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB00999G, Paper