Regio‐ and Stereoselectivity of the SiO<sub>2</sub>‐Catalyzed Reaction of Thiocamphor (=1,7,7‐Trimethylbicyclo[2.2.1]heptane‐2‐thione) with Optically Active Monosubstituted Oxiranes
Bibliographic record
Abstract
Abstract The reactions of the enolizable thioketone (1 R ,4 R )‐thiocamphor (=(1 R ,4 R )‐1,7,7‐trimethylbicyclo[2.2.1]heptane‐2‐thione; 1 ) with ( S )‐2‐methyloxirane ( 2 ) in the presence of a Lewis acid such as SnCl 4 or SiO 2 in anhydrous CH 2 Cl 2 led to two diastereoisomeric spirocyclic 1,3‐oxathiolanes 3 and 4 with the Me group at C(5′), as well as the isomeric β ‐hydroxy thioether 5 ( Scheme 2 ). The analogous reactions of 1 with ( RS )‐, ( R )‐, and ( S )‐2‐phenyloxirane ( 7 ) yielded two isomeric spirocyclic 1,3‐oxathiolanes 8 and 9 with Ph at C(4′), an additional isomer 13 bearing the Ph group at C(5′), and three isomeric β ‐hydroxy thioethers 10, 11 , and 12 ( Scheme 4 ). In the presence of HCl, the β ‐hydroxy thioethers 5, 10, 11 , and 12 isomerized to the corresponding 1,3‐oxathiolanes 3 and 4 ( Scheme 3 ), and 8, 9 , and 13 , respectively ( Scheme 5 ). Under similar conditions, an epimerization of 3, 8 , and 9 occurred to yield the corresponding diastereoisomers 4, 14 , and 15 , respectively ( Schemes 3 and 6 ). The structures of 9 and 15 were confirmed by X‐ray crystallography ( Figs. 1 and 2 ). These results show that the Lewis acid‐catalyzed addition of oxiranes to enolizable thioketones proceeds with high regio‐ and stereoselectivity via an S n 2‐type mechanism.
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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 | 0.000 | 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) | 0.002 | 0.001 |
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".