Influence of solvent polarity on the stereoselectivity of the uncatalyzed [4+2] cycloaddition of cyclopentadiene to an <i>N</i>,<i>N</i>′‐fumaroyl bis‐(six‐membered ring [(2<i>R</i>)‐10a‐homobornane‐10a,2‐sultam])
Bibliographic record
Abstract
Abstract A new six‐membered ring (2R)‐bornane‐10a,2‐sultam was tested as chiral auxiliary for the [4+2] cycloaddition of cyclopentadiene to the bis‐fumaroyl derivative (−)‐1f and shows under chelating conditions similar complete selectivity to Oppolzer's sultam. Inversion of the π‐face selectivity is nevertheless observed under uncatalyzed conditions under the influence of solvent polarity, varying from 82% de for the (2R,3R) cycloadduct 2f in trifluoroethanol to 70% de in favour of the (2S,3S) diastereoisomer in hexane as solvent. A predictive linear correlation is observed between the stereoselectivity and the solvent parameters according to the Abboud–Abraham–Kamlet‐Taft model. PM3 calculations allowed a rationalization of these results based on the transition‐state dipole moment. Illustrated by an x‐ray analysis of cycloadduct (2S,3S)‐2f, the main structural differences and influences in terms of steric and stereoelectronic factors are discussed by comparison of the five‐ versus six‐membered ring homologues. Copyright © 2003 John Wiley & Sons, Ltd.
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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) | 0.003 | 0.001 |
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".