Synthesis and Lewis acid induced isomerization of mono-, di-, and tri-spiro α-keto tetrahydro-furans and -pyrans
Bibliographic record
Abstract
The stereoselectivity of the acid-catalyzed ring expansion of dihydrofuranyl and dihydropyranyl 1,2-adducts to spirocyclic ketones 8 and 9 has been examined. These substrates have become readily available by the utilization of 1,3-dichloroacetone as a synthetic equivalent of cyclopropanone. The kinetically controlled isomerizations result in ring expansion to dispirocyclopentanones. Third-stage conversion to trispirocyclohexanones was shown to be possible in select examples. On a different front, the syn and anti pairs proved capable of interconversion by heating in the presence of boron trifluoride etherate. A push–pull fragmentation of the ketone ring is proposed to account for these epimerizations. Calculations have been performed to simulate transition state energies in the oxonium ion intermediates and to gain some idea of the preferred ground-state geometries of the final products.Key words: oxonium ion rearrangements, ring expansions, acid-catalyzed epimerizations, cyclopropanone equivalent, spirocyclic ethers.
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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 | 0.000 | 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) | 0.000 | 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".