[5 + 1 + 2 + 1] vs [5 + 1 + 1 + 2] Rhodium-Catalyzed Cycloaddition Reactions of Vinylcyclopropanes with Terminal Alkynes and Carbon Monoxide: Density Functional Theory Investigations of Convergent Mechanistic Pathways and Reaction Regioselectivity
Bibliographic record
Abstract
The mechanism of the Rh-catalyzed [5 + 1 + 2 + 1] cycloaddition of VCPs, terminal alkynes, and CO to yield hydroxydihydroindanones has been investigated by ωB97XD/SDD-6-31G* DFT calculations. The study has revealed the existence of two convergent cycloaddition pathways, [5 + 1 + 2 + 1] and [5 + 1 + 1 + 2], differing by only 2 kcal/mol. Both metal-catalyzed and off-metal electrocyclization/aromatization mechanisms for the final bicyclization reaction were investigated, with the traditional acid-catalyzed pathway dominating. The catalytic cycle is limited by the rate of alkyne insertion, which is consistent with mechanistic studies of the related [5 + 2] cycloaddition reaction. Monosubstituted alkyne insertion regioselectivity is kinetically controlled, with insertion via the unsubstituted alkyne terminus predominating. The alkyne insertion process does not appear to be sensitive to steric effects, with both the propyne and phenylacetylene model alkynes showing similar selectivities (TS energy differences of ca. 5 kcal/mol in both cases for the two regioisomeric transition states). C–C bond activation of disubstituted vinylcyclopropanes was investigated, suggesting that activation of the least substituted C–C bond is preferred unless an electron-withdrawing group is present on the VCP, in which case the most substituted bond will be cleaved.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".