Asymmetric Methoxyselenenylations and Cyclizations with 3-Camphorseleno Electrophiles Containing Oxime Substituents at C-2. Formation of an Unusual Oxaselenazole from an Oxime-Substituted Selenenyl Bromide
Bibliographic record
Abstract
Di[(1R)-2-Oximo-endo-3-bornyl] diselenide (4) and its benzoate derivative 5 were prepared from the corresponding known 2-keto diselenide 1. Treatment of 4 and 5 with bromine, followed by silver triflate in methanol-dichloromethane, generated the corresponding selenenyl triflates 6b and 7b. The latter reagents reacted with a variety of mono-, di-, and trisubstituted alkenes to afford the corresponding 1,2-addition products (beta-methoxy selenides) in a highly diastereoselective manner. The free oxime 6b was particularly effective in such methoxyselenenylations, giving diastereomeric ratios (d.r.s) ranging from 86:14 to > 98:2. Even cis-disubstituted alkenes, which typically give poor d.r.s in similar additions with other chiral selenium electrophiles, underwent highly stereoselective additions with this reagent. Reductive deselenizations of the adducts obtained from styrene and cis- and trans-stilbene provided the corresponding methyl ethers, whose absolute configurations were determined by comparison with authentic samples. As expected, the dominant enantiomers thus obtained from cis- and trans-stilbene, using either 6b or 7b, had opposite configurations. Moreover, each geometrical isomer of stilbene produced methyl ethers with the same configuration when treated with either the oxime 6b or the benzoate 7b. Coordination effects between the substituents at the 2-position of the camphor molecule and the positive selenium atoms in the intermediate seleniranium ions are believed to play an important role in determining the stereochemical outcome of methoxyselenenylations. Selenenyl triflate 6b and selenenyl chloride 7c were also investigated in the electrophilic cyclizations of several unsaturated alcohols and carboxylic acids. However, diastereoselectivities were typically much lower than in the methoxyselenenylations. When the selenenyl bromide 6a, derived from the addition of bromine to the corresponding diselenide 4, was allowed to stand in the absence of an alkene, it underwent intramolecular cyclization with the oxime hydroxyl group, followed by further bromination, to afford the unusual oxaselenazole 11, whose structure was determined by spectroscopic means as well as by X-ray crystallography.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".