Syn−Anti Isomerization of Aldols by Enolization
Bibliographic record
Abstract
A variety of aldol adducts are shown to undergo efficient syn-anti isomerization in the presence of imidazole by an enolization mechanism. Isomerizations are high yielding and occur with little or none of the usual byproducts arising from competing elimination or retroaldol reactions. Most substrates reach equilibrium within 0.3-3 days at ambient temperature in chloroform, benzene, or dichloromethane containing 0.3-1 M imidazole. The process is particularly facile for aldols derived from tetrahydro-4H-thiopyran-4-one with rate constants for equilibration varying over ca. 1 order of magnitude for the adducts studied; structurally related aldols derived from cyclohexanone isomerized ca. 3-4 times slower. Isomerization of the acyclic aldol 5-hydroxy-4-methyl-5-phenyl-3-pentanone required heating to 60 degrees C but was achieved with minimal (<5%) retroaldol or elimination. A methoxymethyl ether derivative isomerized 30-40 times slower than the parent aldol. Isomerization of alpha,alpha'-disubstituted aldols and alpha,alpha'-bisaldols indicated low regioselectivity in the enolization. The synthetic utility of the process was demonstrated with the effective preparation of aldol stereoisomers unobtainable by direct methods.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| 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) | 0.005 | 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 teacher head, 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".