Regio‐ and Stereoselective 1,3‐Oxathiolane Formation in the Reaction of Thiolactones with Optically Active Oxiranes
Bibliographic record
Abstract
Abstract The reactions of 3 H ‐isobenzofuran‐1‐thione ( 1 ) with ( S )‐2‐methyloxirane ( 2 ) and ( R )‐2‐phenyloxirane ( 6 ) in the presence of SiO 2 in anhydrous CH 2 Cl 2 led to two pairs of diastereoisomeric spirocyclic 1,3‐oxathiolanes, i.e. , 3 and 4 with a Me group at C(5′), and 7 and 8 with a Ph group at C(4′), respectively ( Schemes 2 and 3 ). In both cases, 3 H ‐isobenzofuran‐1‐one ( 5 ) was formed as a main product. The analogous reactions of 3,4‐dihydro‐2 H‐ [1]benzopyran‐2‐thione ( 9 ) and 3,4,5,6‐tetrahydro‐2 H ‐pyran‐2‐thione ( 14 ) with 2 and 6 yielded four pairs of the corresponding diastereoisomeric spirocyclic compounds 10 and 11, 12 and 13, 15 and 16 , and 18 and 19 , respectively ( Schemes 4–7 ). In the reaction of 14 with 6 , the 1,3‐oxathiolane 20 with a Ph group at C(2) was also formed. The structures of 3, 7, 8, 10, 19 , and 20 were established by X‐ray crystallography ( Figs. 1–4 ). In contrast to the thiolactones 1, 9 , and 14 , the thioesters 21a – 21d did not react with ( R )‐2‐phenyloxirane ( 6 ) either in the presence of SiO 2 or under more‐drastic conditions with BF 3 ⋅Et 2 O or SnCl 4 ( Scheme 8 ). The results show that spirocyclic 1,3‐oxathiolanes can be prepared from thiolactones with oxiranes. The nucleophilic attack of the thiocarbonyl S‐atom at the SiO 2 ‐activated oxirane ring 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) | 0.001 | 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".