Hydrogen Atom Transfer-Based C(sp<sup>3</sup>)–H Bond Oxygenation of Lactams and Cycloalkenes: The Influence of Ring Size on Reactivity and Site Selectivity
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide Kinetic and product studies on the reactions of the cumyloxyl (CumO • ) and tert -butoxyl ( t BuO • ) radicals with secondary and tertiary N -methyl and N -benzyl lactams and with cycloalkenes, accompanied by BDE calculations of the substrate C–H bonds involved in these reactions, are reported. Within the lactams, the rate constants for HAT ( k H ) from the C–H bonds to CumO • decrease by a factor ∼4 going from the 5- and 6-membered derivatives to the 8-membered ones. Product distributions obtained through oxygenation initiated by t BuO • show that HAT preferentially occurs from the most electron-rich α-C–H bonds, with site selectivity that, within the N -methyl and N -benzyl series, progressively shifts from the endocyclic to the exocyclic α-C–H bonds with increasing ring size, indicative of deactivation of the former bonds that, for the 8-membered derivatives, translates into competitive oxygenation at different sites. Similar trends have been observed for the corresponding reactions of the cycloalkenes, with k H values that decrease by a factor of ∼4 together with site selectivity for HAT from the activated allylic C–H bonds, going from cyclopentene to cyclooctene. It is proposed that the greater flexibility of the medium-sized rings decreases the extent of hyperconjugative overlap between the α-C–H bonds and the amide or C═C π-systems, increasing the kinetic barrier for HAT from these sites, with decreases in reactivity that approach factors of 83 and 18, for the endocyclic α-C–H bonds of tertiary N -methyl lactams and the allylic C–H bonds of cycloalkenes, respectively.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".