Mechanisms of Intramolecular Rearrangements of Cyclic Siloxycarbenes
Bibliographic record
Abstract
Intramolecular rearrangements of 3-sila-2-oxacyclohexylidene have been investigated using hybrid density functional theory calculations, the quantum theory of atoms in molecules, and the electron localization function. Mechanisms for 1,2-H migration, ring contraction, and decarbonylation have been examined. The mechanism for 1,2-H migration was shown to involve a typical hydride-like shift from the migration origin to the “vacant” carbene p orbital, while ring contraction was found to occur via a concerted pathway involving a front-side nucleophilic attack by the carbene lone pair at silicon as opposed to a stepwise pathway involving an acyl−silyl biradical intermediate. Decarbonylation, on the other hand, was shown to be a stepwise reaction that preferentially occurs via the intermediacy of silacyclopentanone rather than acyl−silyl and alkyl−silyl biradicals. Computed energetics and thermodynamics indicate that 1,2-H migration and ring contraction are considerably more favorable than decarbonylation. Finally, AIM analysis reveals that the changes in molecular structure associated with 1,2-H migration involving a hydride-like shift to the “vacant” carbene p orbital occur via a conflict mechanism, whereas those associated with ring contraction (or 1,2-silyl migration) involving front-side nucleophilic attack by the carbene lone pair at silicon occur via a bifurcation mechanism . The latter findings further suggest that AIM analysis may be a viable approach to unambiguously distinguish between reaction mechanisms.
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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) | 0.005 | 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".