A Mechanistic Study of the Stereochemical Outcomes of Rhodium‐Catalysed Styrene Aziridinations
Bibliographic record
Abstract
Abstract The stereoselective, rhodium‐catalysed aziridination of styrene derivatives with a chiral N ‐mesyloxycarbamate was found to be highly substrate dependent. A density functional theory (DFT) study is herein reported to elucidate the stereochemical outcome of the aziridination process. Rhodium acetate was initially used as a model catalyst, followed by computational studies conducted with Rh 2 [( S )‐nttl] 4 . Both singlet and triplet rhodium nitrene species were identified as intermediates affording concomitant concerted and radical pathways. In the latter case, the radical intermediate appears to undergo a direct ring closure via a minimum energy crossing point (MECP) between the triplet and closed‐shell singlet surfaces. Exceptionally for the m ‐Br‐styrene aziridination, an alternative radical pathway with a carbon‐carbon bond rotation was observed, accounting for the observed 74:26 mixture of diastereomers. The computational analysis also suggests little control of the metal nitrene conformation with Rh 2 (OAc) 4 with the chiral N ‐mesyloxycarbamate: two conformers were located affording two diastereomers of the aziridine and correlating our experimental results. On the other hand, only one conformer was found for the nitrene generated from the chiral N ‐mesyloxycarbamate and Rh 2 [( S )‐nttl] 4 . The so‐called “all‐up” conformer of Rh 2 [( S )‐nttl] 4 was not only the most stable metal nitrene species, but also afforded the lowest energy transition state. The calculated dr for p ‐Br‐styrene aziridination agrees with the observed experimental result. The combination of experimental and computational results offers a detailed mechanistic picture, providing insights for further catalyst development to enhance reactivity and selectivity. magnified image
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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".