A versatile method for the synthesis of γ-pyrones
Bibliographic record
Abstract
A versatile three-step procedure to annulate a γ-pyrone onto a methylene ketone was developed involving (i) aldol reaction with a dithiolane-protected β-ketoaldehyde, (ii) oxidation of the aldol adduct to a β-diketone, and (iii) treatment of the resulting dithiolane-protected 1,3,5-trione with 2-iodoxybenzoic acid (IBX) and trifluoromethanesulfonic acid (triflic acid; TfOH) in acetonitrile at ambient temperature to give the corresponding γ-pyrone. Cyclization proceeded with IBX alone, but significantly improved yields were obtained with added acid, particularly triflic acid. A dithiolane was more effective than a dithiane or acyclic dithioacetal protecting group. The method was amenable to the preparation of a variety of substituted γ-pyrones simply by altering the initial aldol reactants. Overall yields of 50%–60% were obtained in six examples. The method was applied to prepare a key fragment for the total synthesis of baconipyrones A and C and siphonarin B.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.002 |
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".