Hydrogen Atom Transfer from Alkanols and Alkanediols to the Cumyloxyl Radical: Kinetic Evaluation of the Contribution of α-C-H Activation and β-C-H Deactivation
Salamone, M; Ortega, VB; Martin, T; Bietti, M
| HERO ID | 4854530 |
|---|---|
| In Press | No |
| Year | 2018 |
| Title | Hydrogen Atom Transfer from Alkanols and Alkanediols to the Cumyloxyl Radical: Kinetic Evaluation of the Contribution of α-C-H Activation and β-C-H Deactivation |
| Authors | Salamone, M; Ortega, VB; Martin, T; Bietti, M |
| Journal | Journal of Organic Chemistry |
| Volume | 83 |
| Issue | 10 |
| Page Numbers | 5539-5545 |
| Abstract | A kinetic study on the reactions of the cumyloxyl radical (CumO•) with a series of alkanols and alkanediols has been carried out. Predominant hydrogen atom transfer (HAT) from the α-C-H bonds of these substrates, activated by the presence of the OH group, is observed. The comparable kH values measured for ethanol and 1-propanol and the increase in kH measured upon going from 1,2-diols to structurally related 1,3- and 1,4-diols is indicative of β-C-H deactivation toward HAT to the electrophilic CumO•, determined by the electron-withdrawing character of the OH group. No analogous deactivation is observed for the corresponding diamines, in agreement with the weaker electron-withdrawing character of the NH2 group. The significantly lower kH values measured for reaction of CumO• with densely oxygenated methyl pyranosides as compared to cyclohexanol derivatives highlights the role of β-C-H deactivation. The contribution of torsional effects on reactivity is evidenced by the ∼2-fold increase in kH observed upon going from the trans isomers of 4- tert-butylcyclohexanol and 1,2- and 1,4-cyclohexanediol to the corresponding cis isomers. These results provide an evaluation of the role of electronic and torsional effects on HAT reactions from alcohols and diols to CumO•, uncovering moreover β-C-H deactivation as a relevant contributor in defining site selectivity. |
| Doi | 10.1021/acs.joc.8b00562 |
| Pmid | 29668277 |
| Wosid | WOS:000432900800020 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |