6-Lithio-2,3-dihydro-4<i>H</i>-pyran
Bibliographic record
Abstract
[72081-15-3] C5H7LiO (MW 90.05) (acyl anion equivalent which reacts with a variety of carbon and other electrophiles via substitution and 1,2-addition;2-6 after conversion to other organometallics via conjugate addition7 and Pd0-catalyzed coupling,5 the resulting adducts are utilized for the preparation of substituted cyclopentenones and cyclohexenones and polycyclic spiro acetals2-9) Alternate Name: 6-lithio-3,4-dihydro-2H-pyran. Physical Data: white to off-white, highly moisture and air sensitive solid which may be pyrophoric.10 13C NMR (22.625 MHz in d8 THF): δ 201.2, 111.1 , 62.8, 24.71, 20.99.10 Solubility: sol anhydrous THF, anhydrous ether, and mixtures of saturated hydrocarbons and THF; insol pure hydrocarbons. At high concentrations (> ca. 1M), the reagent will sometimes precipitate from THF–pentanes at −78 °C. Form Supplied in: not commercially available. Analysis of Reagent Purity: the extent of metalation can be assessed by deuteration of an aliquot and 1H NMR analysis of the recovered 2,3-dihydropyran,10 or by direct observation using 1H NMR.2, 11 The concentration of solutions of the reagent can be determined by titration.12 Preparative Methods: three basic preparative methods have been described: metalation with the t-BuLi–2THF complex (lemon yellow) in pentane at about −10 °C;2 metalation with n-BuLi or t-BuLi in hexane or pentane containing a catalytic amount of TMEDA at 0 °C to room temperature or slightly above (the reagent precipitates from solution);10, 13 or metalation with n-BuLi in hexanes at 50–60 °C for several hours (also results in a precipate of the lithium reagent).14 For difficult cases, the Schlosser base (n-BuLi/KO-t-Bu) has been used, usually followed by trapping with chlorotrialkylstannanes and transmetalation of 6-trialkylstannyl-2,3-dihydro-4H-pyran and substituted derivatives thereof with n-BuLi in THF at −78 °C,8, 15-21 or by palladium-catalyzed coupling of chlorotrialkylstannanes with enol triflates derived from δ-lactones.22 Purification: none is normally required; the reagent is used as prepared. Handling, Storage, and Precautions: the reagent is customarily utilized shortly after preparation. Solvents and reagents should be anhydrous and free of oxygen. Commercial 2,3-dihydropyran is distilled before use. Solutions of the reagent must be protected from air and moisture utilizing standard inert atmosphere/syringe techniques.
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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 | 0.007 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.003 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.068 | 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; both teacher heads agree on what is shown here.
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".