N‐Heteroarylation of Optically Pure α‐Amino Esters using the Pd‐PEPPSI‐IPent<sup>Cl</sup>‐<i>o</i>‐picoline Pre‐Catalyst
Bibliographic record
Abstract
Abstract A robust, mild, and efficient method for the Pd‐catalyzed N‐heteroarylation of optically pure α‐amino esters was developed. Dichloro[1,3‐bis(2,6‐di‐3‐pentylphenyl)imidazol‐2‐ylidene]( o ‐picoline)palladium(II) (Pd‐PEPPSI‐IPent Cl ‐ o ‐picoline; PEPPSI=pyridine enhanced pre‐catalyst preparation, stabilization, and initiation) was shown to effectively couple a variety of amino acids as the tert ‐butyl ester with heteroaryl chlorides in high yields and with excellent stereoretention of the acidic proton adjacent to the ester. Control experiments revealed that racemization is base‐mediated, with no evidence of Pd‐mediated β‐hydride elimination when using Pd‐PEPPSI‐IPent Cl , and that racemization occurs only after the product is formed, that is, the non‐arylated starting amino ester does not deprotonate under our reaction conditions. Studies also revealed that increasing the steric bulk of the ester moiety on the amino acid (e.g., ethyl to tert ‐butyl) drastically slows racemization of the product.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".