Rhodium(III)-Catalyzed Heterocycle Synthesis Using an Internal Oxidant: Improved Reactivity and Mechanistic Studies
Bibliographic record
Abstract
Directing groups that can act as internal oxidants have recently been shown to be beneficial in metal-catalyzed heterocycle syntheses that undergo C-H functionalization. Pursuant to the rhodium(III)-catalyzed redox-neutral isoquinolone synthesis that we recently reported, we present in this article the development of a more reactive internal oxidant/directing group that can promote the formation of a wide variety of isoquinolones at room temperature while employing low catalyst loadings (0.5 mol %). In contrast to previously reported oxidative rhodium(III)-catalyzed heterocycle syntheses, the new conditions allow for the first time the use of terminal alkynes. Also, it is shown that the use of alkenes, including ethylene, instead of alkynes leads to the room temperature formation of 3,4-dihydroisoquinolones. Mechanistic investigations of this new system point to a change in the turnover limiting step of the catalytic cycle relative to the previously reported conditions. Concerted metalation-deprotonation (CMD) is now proposed to be the turnover limiting step. In addition, DFT calculations conducted on this system agree with a stepwise C-N bond reductive elimination/N-O bond oxidative addition mechanism to afford the desired heterocycle. Concepts highlighted by the calculations were found to be consistent with experimental results.
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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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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; 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".