Is Schleyer’s Predicted All-Cis [10]Annulene an Unstable Framework?
Bibliographic record
Abstract
In this work we describe the synthesis of a long sought after planar [10]annulene. Remarkably, the efforts also led us to discover a completely unexpected and highly aromatic cyclopropa mono-trans[10]annulene. The parent [10]annulene (cyclodecapentaene) is non-planar and thus non-aromatic because the aromatic stabilization energy is not sufficient to overcome the strain involved in expanding CCC bond angles from the standard 120° to the necessary 144°. Interestingly, it was theorized by Schleyer (10.1021/ja953126i) that planar structures could be attained by adding cyclopropane (or cyclobutane) rings to the periphery. We opted to target the dicyclopropa[10]annulene derivative that was proposed as it was a formal cyclopropanation of our previously found stable dehydrocyclopropa[10]annulene (10.1038/s44160-022-00135-z, 10.26434/chemrxiv.14458653.v1). It was also presumed that the symmetry present within the structure would make the Kekulé structures degenerate, thus improving aromaticity substantially. However, we were uncertain if the structure would be kinetically stable and wished to attempt a synthesis to investigate it further. In this paper we describe our evolving synthetic strategy that ultimately led us to the preparation of the dicyclopropa[10]annulene. Interestingly we noted that the framework itself was rather unstable and degraded quite rapidly. We also observed that the final preparation of the desired material led to a significant side product that was identified as a cyclopropa mono-trans[10]annulene. This side product was completely unexpected and found to be more kinetically persistent than the original target.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".