Modular <i>P</i>-Chirogenic Phosphine-Sulfide Ligands: Clear Evidence for Both Electronic Effect and <i>P</i>-Chirality Driving Enantioselectivity in Palladium-Catalyzed Allylations
Bibliographic record
Abstract
Using the ephedrine methodology, modular stereoselective syntheses of a new class of P -chirogenic phosphines bearing a sulfur-chelating arm (P*,S-hybrid ligand) are described. A first series of syntheses based on a Fries-like rearrangement of P -chirogenic phosphinite-boranes, which are prepared from 2-bromobenzyl or 2-bromophenethyl alcohol and are mediated by metal–halide exchange, have been performed. This rearrangement affords phosphine-boranes stereospecifically with an o -hydroxyalkylphenyl substituent. The latter residue is subsequently converted into a sulfur-containing group. In a second series, the stereoselective syntheses were achieved according to a new strategy involving a reaction of a thiophenyllithium reagent with a P -chirogenic phosphinite. The X-ray structures of the P*,S ligands and their palladium complexes allow us to address the absolute configuration at both the phosphorus and sulfur centers. The P*,S ligands were used in palladium-catalyzed allylic alkylations, as tests, affording asymmetric inductions up to 96% ee. Computer modeling corroborates the regio- and enantioselectivity of the Pd-catalyzed allylations and the low influence of the substituent carried by the sulfur moiety, particularly when the chelate forms a six-membered ring with the metal.
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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) | 0.000 | 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) | 0.001 | 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 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".