Metal Coordination Controlled and Bifunctional H‐Bonded Catalysis in Stereoselective Intramolecular Aldol Cyclizations toward Carbocyclic Tertiary β‐Ketols
Bibliographic record
Abstract
The principle of bifunctional catalysis is shown in the highly regio‐ and stereoselective intramolecular aldolization of 2‐methyl‐1,3‐cyclopentanedione, C2‐substituted with a methyl ethyl ketone group, to provide [3.2.1]‐bicyclooctanol diones in the presence of catalytic amounts of either LiBr and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), or 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD). Mechanistic investigations corroborated by DFT calculations show that LiBr engages in a bifunctional coordination of two carbonyl moieties and leads to the preorganization of the reactive enolate intermediate for a base‐mediated intramolecular aldol cyclization. On the other hand, TBD catalysis of the triketone substrate proceeds through a bifunctional H‐bonded mechanism to give the same aldol product as the major diastereomer. The LiBr and TBD‐catalyzed highly stereocontrolled intramolecular aldol cyclizations can be extended to other di‐ and triketones to give carbocyclic and carbobicyclic products as single diastereomers.
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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".