| Autor: |
Kolmar SS; Department of Chemistry, Yale University , New Haven, Connecticut 06520, United States., Mayer JM; Department of Chemistry, Yale University , New Haven, Connecticut 06520, United States. |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2017 Aug 09; Vol. 139 (31), pp. 10687-10692. Date of Electronic Publication: 2017 Jul 31. |
| DOI: |
10.1021/jacs.7b03667 |
| Abstrakt: |
Samarium diiodide in the presence of water and THF (SmI 2 (H 2 O) n ) has in recent years become a versatile and useful reagent, mainly for reducing carbonyl-type substrates. This work reports the reduction of several enamines by SmI 2 (H 2 O) n . Mechanistic experiments implicate a concerted proton-coupled electron transfer (PCET) pathway, based on various pieces of evidence against initial outer-sphere electron transfer, proton transfer, or substrate coordination. A thermochemical analysis indicates that the C-H bond formed in the rate-determining step has a bond dissociation free energy (BDFE) of ∼32 kcal mol -1 . The O-H BDFE of the samarium aquo ion is estimated to be 26 kcal mol -1 , which is among the weakest known X-H bonds of stable reagents. Thus, SmI 2 (H 2 O) n should be able to form very weak C-H bonds. The reduction of these highly electron rich substrates by SmI 2 (H 2 O) n shows that this reagent is a very strong hydrogen atom donor as well as an outer-sphere reductant. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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