Stoichiometric Reactivity Relevant to the Mor-DalPhos/Pd-Catalyzed Cross-Coupling of Ammonia and 1-Bromo-2-(phenylethynyl)benzene
Bibliographic record
Abstract
While Mor-DalPhos/Pd precatalyst mixtures have in general proven to be highly effective for the monoarylation of ammonia employing a range of (hetero)aryl (pseudo)halide cross-coupling partners, we have observed previously that 1-bromo-2-(phenylethynyl)benzene (Ar*Br) is a challenging substrate for this catalyst system. We report herein on our efforts to examine some possible modes of catalyst inhibition by this substrate. Treatment of [CpPd(allyl)] with Mor-DalPhos in the presence of Ar*Br afforded [(κ 2 - P, N -Mor-DalPhos)Pd(Br)(Ar*)] ( 1; 85%), which was transformed into [(κ 3 - P, N,O -Mor-DalPhos)Pd(Ar*)] + OTf – ( 3; 83%) upon treatment with AgOTf. The characterization of 3 establishes the ability of the Mor-DalPhos ligand to adopt a κ 3 -P,N,O structure, which may influence the course of some Pd-catalyzed amination processes. While treatment of 1 with AgOTf in the presence of ammonia, or alternatively treatment of 3 with ammonia, resulted in the clean formation of [(κ 2 - P, N -Mor-DalPhos)Pd(NH 3 )(Ar*)] + OTf – ( 2 ), our efforts to isolate this compound were thwarted by the facile loss of ammonia from 2 to give 3 . Neither NMR spectroscopic nor X-ray crystallographic data obtained for 1 and 3 support the existence of significant Pd···alkyne interactions in these complexes. Treatment of the Pd(0) species [L 2 Pd(diphenylacetylene)] (L 2 = Mor-DalPhos, 4; L 2 = CyPF t Bu-JosiPhos, 5 ) with Ar*Br resulted in divergent behavior: while multiple phosphorus-containing products were observed in the case of 4, under analogous conditions 5 was transformed cleanly into [(κ 2 - P, P -JosiPhos)Pd(Br)(Ar*)] ( 6 ). The identification of 6 was facilitated via independent synthesis from Ar*Br, JosiPhos, and [CpPd(allyl)] (90%). These observations suggest that the inferior performance of Mor-DalPhos relative to JosiPhos in the arylation of ammonia using Ar*Br may be attributable in part to the inefficiency with which putative [(Mor-DalPhos)Pd(alkyne)] species re-enter the catalytic cycle via C–Br oxidative addition.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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".