Design considerations for chiral frustrated Lewis pairs: B/N FLPs derived from 3,5-bicyclic aryl piperidines
Bibliographic record
Abstract
Herein, 3,5-bicyclic aryl piperidines are derivatized to generate chiral B/N FLPs. Initially, the twofold symmetric amine C6H2F2(C5H8NiPr) 1 was converted in a series of synthetic steps to the styrene-derivative C6HF2(C5H8NiPr)(CH[double bond, length as m-dash]CH2) 4. Efforts to hydroborate the vinyl fragment proved challenging as a result of the strongly basic nitrogen, although the species C6HF2(C5H8N(H)iPr)(CH2CH2B(OH)(C6F5)2) 5 was crystallographically characterized. Modification of the system was achieved by conversion of the amine C6H2F2(C5H8NH) 6 to C6HF2(C5H8NPh)(CH[double bond, length as m-dash]CH2) 9. Hydroboration of 9 with 9-BBN or HB(C6F5)2 gave C6HF2(C5H8NPh)(CH2CH2BBN) 10 or C6HF2(C5H8NPh)(CH2CH2B(C6F5)2) 11, respectively. The latter species was derivatized by complexation of PPh3 to give C6HF2(C5H8NPh)(CH2CH2B(C6F5)2)(PPh3) 12. The Lewis acidities of 10 and 11 were assessed by the Gutman-Beckett test and by computations of the FIA and GEI. While 10 did not effect HD scrambling or hydrogenation of N-phenylbenzylimine, 11 was effective in HD scrambling. Despite this, no reduction of N-t-butylbenzylimine or N-phenylbenzylimine was achieved. These data demonstrate that 10 lacks the threshold combination of Lewis acidity and basicity to activate H2, while 11 lacks the steric demands about boron to preclude classical Lewis acid-base bond formation with imine substrates.
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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 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".