Bibliographic record
Abstract
An overview is given of the use of the Heck reaction for the production of fine chemicals. Five commercial products have been identified that are produced on a scale in excess of 1 ton/year. The herbicide Prosulfuron(tm) is produced via a Matsuda reaction of 2-sulfonatobenzenediazonium on 3,3,3-trifluoropropene. The sunscreen agent 2-ethylhexyl p-methoxy-cinnamate has been produced on pilot scale using Pd/C as catalyst. Naproxen(tm) is produced via the Heck reaction of 2-bromo-6-methoxy-naphthalene on ethylene, followed by carbonylation of the product. Monomers for coatings are produced via a Heck reaction on 2-bromo-benzocyclobutene. A key step in the production of the antiasthma agent Singulair(tm) is the use of the Heck reaction of methyl 2-iodo-benzoate on allylic alcohol (18) to give ketone (20). The high cost of palladium has spurred much research aimed at the development of more active palladium catalysts. Ligandless catalysts are very attractive for production, but work only on reactive substrates. Palladacycles are much more stable than Pd-phosphine complexes and can be used at higher temperatures. The same effect has been reached with pincer ligands. Bulky ligands lead to coordinatively unsaturated Pd-complexes, which are highly active for the Heck reaction. Recycle of palladium catalysts is also very important to reduce cost. Immobilization of catalysts by attaching ligands to solid support is not very useful, because of leaching and reduced activity. In ligandless Heck reactions the catalyst can be precipitated on carriers such as silica, dicalite, or celite. This material can be restored to its original activity by treatment with I2 or Br2.Key words: homogeneous catalysis, palladium, arylation, olefination, ligandless, catalyst recycle.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.004 |
| Insufficient payload (model declined to judge) | 0.012 | 0.020 |
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".