Stereoselective Synthesis of <i>N</i>‐Propargyl Alkynes and Axial Chiral <i>N</i>‐Allenes with Epimeric Pyrroloimidazolone Auxiliaries
Bibliographic record
Abstract
Abstract An N ‐propargyl pyrroloimidazolone with syn stereochemistry derived from L‐proline serves as a starting material for the diastereoselective synthesis (>95:5 dr) of propargyl alkynes or allenamides by direct quench of its lithiated intermediate with alkylating agents or aldehydes/ketones, respectively. Use of the epimeric anti pyrroloimidazolone starting material results in reversal of stereochemistry at the propargyl position in the products, without the need to prepare a separate substrate from D‐proline. Lithiation of the syn pyrroloimidazolone and quench with prochiral benzaldehydes without prior transmetalation gives allenamides with crystallographically verified atypical stereochemistry of the benzylic alcohol in >95:5 dr. The epimeric series of benzylic alcohols may also be obtained in >95:5 dr by employing transmetalation with chlorotitanium triisopropoxide prior to aldehyde quench. Density Functional Theory (DFT) computational studies provide a rationale for the change in benzylic alcohol stereochemistry by virtue of differing stereofacial attack in 6,5‐bicyclic (Li) or 6‐membered (Ti) transition states. magnified image
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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) | 0.003 | 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".