Activation and Deactivation of Benzylic C−H Bonds Guided by Stereoelectronic Effects in Hydrogen Atom Transfer from Amides and Amines to Alkoxyl Radicals
Bibliographic record
Abstract
Abstract Kinetic and product studies on the reactions of tert‐alkoxyl radicals with secondary and tertiary alkanamides bearing benzylic α‐C−H bonds, isoindoline, tetrahydroisoquinoline and the corresponding N‐acetyl derivatives were carried out. Product studies on the reactions with the tert‐butoxyl radical (tBuO⋅) point toward exclusive HAT from the benzylic α‐C−H bonds. Comparison of the kH values measured for reaction with the cumyloxyl radical (CumO⋅) with those obtained previously for the corresponding reactions of N‐alkyl‐ and N,N‐dialkylalkanamides, are indicative of a lack of benzylic activation and the operation of steric and stereoelectronic effects. Compared to N‐methyl and N‐ethyl groups, the presence of N‐benzyl groups increases the barrier required to reach the optimal conformation for HAT, where the α‐C−H bond to be cleaved is perpendicular to the plane of the amide, precluding concurrent overlap with the phenyl π‐system. When the benzylic α‐C−H bonds are in a conformation that allows for optimal overlap with both the phenyl π‐system and the amide π‐system or amine nitrogen lone pair, as in the isoindoline and tetrahydroisoquinoline derivatives, increases in kH that exceed 2‐orders of magnitude were observed, highlighting the strong contribution provided by stereoelectronic activation to these HAT processes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".