A Dipyridoimidazolium Salt from Phenylchlorocarbene and 2,2'‐Bipyridyl: Synthesis, Reaction Mechanism, and Effect of Rotamerism
Bibliographic record
Abstract
Abstract Phenylchlorocarbene, generated by photolysis or thermolysis of the phenylchlorodiazirine, reacts with 2,2'‐bipyridyl to give, in alkane solvents, the 6‐phenyldipyrido[1,2‐c:2',1'‐e]imidazolium chloride. We investigated the mechanism of the reaction by flash photolysis. Like the mechanism of formation of 3‐phenylindolizine from phenylchlorocarbene + 2‐vinylpyridine, the process involves generation of the carbene, formation of a pyridinium ylide, and cyclization of the syn rotamer of this ylide, with the two N atoms of the bipyridyl in a syn relationship. The cyclization product then eliminates Cl– to give a stable aromatic cation. We observed and identified all the intermediate species and measured the rate constants for the successive elementary reactions. This enabled us to define experimental conditions under which the reaction is nearly quantitative (the chemical yield of isolated product is >90 %). By contrast, use of a polar solvent such as dichloromethane yields a mixture of the products resulting from the cyclization of both the syn‐ and the anti‐bipyridylium ylide rotamers. Semiempirical calculations qualitatively account for the effect of solvent polarity on the relative rates of cyclization of the syn‐ and anti‐bipyridylium ylide rotamers and thus on the nature of the products. These calculations predict that, in the presence of o‐phenanthroline, a model for the syn bipyridyl rotamer, phenylchlorocarbene should not give the expected diazacyclopentaphenanthrene, in agreement with the experiment findings. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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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) | 0.001 | 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".