Borohydrides from Organic Hydrides: Reactions of Hantzsch’s Esters with B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>
Bibliographic record
Abstract
We report herein that the reaction between a series of Hantzsch's ester analogues 1 a-d with the Lewis acidic species B(C(6)F(5))(3) results in facile transfer of hydride to boron. The main products of this reaction are pyridinium borohydride salts 2 a-d, which are obtained in high to moderate yields. The N-substituted substrates (N-Me, N-Ph) reacted in high yield 90-98 % and the connectivity of the products were confirmed by an X-ray crystallographic analysis of the N-Me borohydride salt 2 a. Unsubstituted Hanztsch's ester 1 a reacted less effectively generating only 60 % of the corresponding borohydride salt, with the balance of the material sequestered as the ester-bound Lewis acid-base adduct 3 a. Formation of the Lewis acid-base adduct could be minimized by increasing the steric bulk about the ester groups as in 1 d. The connectivity of the carbonyl-bound adduct was confirmed by an X-ray crystallographic analysis of 3 e the product of the reaction of methyl ketone 1 e with B(C(6)F(5))(3). We also explored the generation of these pyridinium salts by employing frustrated Lewis pair methodology. However, the reaction of mixtures of the corresponding pyridine and B(C(6)F(5))(3) with hydrogen gas only resulted in formation of trace amounts of the pyridinium borohydride, along with the Lewis acid-base adduct of the starting material and B(C(6)F(5))(3). The 1,2-dihydropyridine adduct was the final product of this reaction. This was ascribed to the low basicity of the pyridine nitrogen and the complicating formation of an ester bound Lewis acid-base adduct.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.004 |
| 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; both teacher heads agree on what is shown here.
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".