Alkenylborane-Derived Frustrated Lewis Pairs: Metal-Free Catalytic Hydrogenation Reactions of Electron-Deficient Alkenes
Bibliographic record
Abstract
A series of alkenylboranes were prepared by 1,1-carboboration routes and used as Lewis acid components for the generation of frustrated Lewis pairs (FLPs). The reactions of 1-alkynes with B(C 6 F 5 ) 3 gave the RCH═C(C 6 F 5 )B(C 6 F 5 ) 2 systems 4a (R = n -C 3 H 7 ), 4b (R = n -C 4 H 9 ), 4c (R = Ph), and 4d (R = t -C 4 H 9 ), respectively. The alkenylborane/ t Bu 3 P FLPs derived from compounds 4a – d reacted rapidly with dihydrogen (2.5 bar) at ambient temperature. The bulky system 4d left the C═C double bond of the alkenylborane unsaturated and gave the dihydrogen cleavage product [ t Bu 3 PH][ t BuCH═C(C 6 F 5 )BH(C 6 F 5 ) 2 ] ( 10d ). In contrast, the less bulky systems 4a / t Bu 3 P and 4b / t Bu 3 P split dihydrogen under these conditions and had their C═C double bonds cleanly reduced to yield the corresponding 1-pentafluorophenylalkyl hydridoborate salts [ t Bu 3 PH][RCH 2 CH(C 6 F 5 )BH(C 6 F 5 ) 2 ] 9a (R = n -C 3 H 7 ) and 9b (R = n -C 4 H 9 ), respectively. The 4c / t Bu 3 P FLP gave a mixture of both product types ( 9c / 10c ). 1,1-Carboboration of symmetrical internal alkynes gave the alkenylboranes R 2 C═C(C 6 F 5 )B(C 6 F 5 ) 2 4e (R = C 2 H 5 ), 4f (R = n -C 3 H 7 ), 4g (R = Ph), and 4h (R = p -MeC 6 H 4 ), respectively. The 4e – h / t Bu 3 P FLPs cleaved dihydrogen under mild conditions but retained their C═C double bonds to give the respective [ t Bu 3 PH][R 2 C═C(C 6 F 5 )BH(C 6 F 5 ) 2 ] products ( 10e – h ). Selected examples of these alkenylboranes undergo FLP reactions acting as catalysts for the hydrogenation of imines. Perhaps most remarkably, some of these alkenylboranes retain the C═C double bonds under FLP/H 2 reaction conditions and heterolytically split dihydrogen in the presence of the Lewis base DABCO and catalyze the hydrogenation of the electron-poor C═C double bonds of diaryl-substituted enones.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".