Issue Date: October 12, 2009
Surprise And Closeness
I always look forward to scanning the Science & Technology Concentrates as part of an effort to keep abreast of recent developments, so I was not completely surprised by the item from a CalTech group titled "Surprise Methyl C–H Activation in DMF" (C&EN, June 15, page 26).
The concluding statement, "The fact that methyl C–H activation can compete at all with activation of the much more reactive aldehydic C–H bond is unexpected and intriguing," is fundamentally correct, while the relevant publication (Organometallics 2009, 28, 4229) states, "To our knowledge there have been no reports of C–H activation of a methyl group of DMF or any closely related species" (my italics). The research involves an Ir species, and DMF is HC(O)NMe2.
However, there is earlier evidence that in the related (how close?) amide species RC(O)NMe2 (R = Me and 4-cyclopentyl), such activation can occur. John M. Brown's group reported NMR data that revealed chelation (also to an Ir center) of the cyclopentyl amide via the carbonyl O-atom and the CH2 formed from one of the Me groups (J. Chem. Soc. Chem. Commun. 1987, 1278), whereas my group invoked such activation to explain formation of the hydroperoxide product, MeC(O)N(Me)CH2OOH, from a Rh-catalyzed hydrogen peroxide oxidation of dimethylacetamide (R = Me) (J. Chem. Soc. Chem. Commun. 1989, 1624).
I consider these earlier studies to involve "related" species, but "close" is impossible to define!
Brian R. James
Vancouver, British Columbia
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