Efficient Synthesis of a <i>C</i><sub>2</sub>‐Symmetric 2,2′‐Bipyridine‐α,α′‐1‐<i>t–</i>butyl‐diol Ligand by Stereoselective Double Hydrogen Transfer to a 2,2′‐Bipyridine‐diketone
Bibliographic record
Abstract
Abstract An efficient and practical method was developed for the synthesis of C2‐symmetric 2,2′‐bipyridine‐α,α′‐1‐t‐butyl‐diol ligands. The disclosed synthesis involves the Ullmann homocoupling of a keto bromo‐pyridine under NiCl2/Zn/PPh3 conditions, followed by the stereoselective double hydrogen transfer to the obtained 2,2′‐bipyridine‐diketone using RuII Noyori–Ikariya catalysts. This approach allowed the successful synthesis of 2,2′‐bipyridine‐α,α′‐1‐t‐butyl‐diol, i.e (S,S)‐Bolm's ligand, with a quantitative yield and an excellent stereoselectivity (ee>99.5 %, de>99.5 %), with an overall yield of 69 % from easily accessible starting materials.
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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) | 0.002 | 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".