2004 Bader Award LectureMetal-ion-catalyzed acyl and phosphoryl transfer reactions to alcohols: La<sup>3+</sup>-promoted alcoholysis of activated amides, carboxylate esters, and neutral organophosphorus esters
Bibliographic record
Abstract
Unlike metal-ion-catalyzed hydrolysis processes, metal-ion-catalyzed methanolysis processes have received scant attention in the literature particularly from the standpoint of mechanistic studies. La 3+ , introduced into methanol solution as its triflate or perchlorate salt, is particularly effective in promoting methanolysis reactions of unactivated and activated esters, phosphate triesters, and activated amides such as acetyl imidazoles and lactams. Studies of the kinetics of methanolysis of these substrates as a function of solution pH and [La 3+ ] indicate that the solution comprises lanthanum dimers with one to five associated methoxides (La 2 3+ ( OCH 3 ) 15 ), the most catalytically active form being La 2 3+ ( OCH 3 ) 2 , which is produced at near neutral pH in methanol (8.4). Mechanisms for all the acyl and phosphoryl transfer reactions are proposed where the metal ion serves a dual role of acting as a Lewis acid to activate the C=O or P=O system to nucleophilic attack by a metal-coordinated methoxide nucleophile. In cases where direct comparisons can be made, the La 2 3+ catalyst system is more active for the methanolysis of nonactivated substrates than for activated substrates. Another general characteristic of this system is that the catalytic rate constant for the metal complex exceeds the second-order rate constant for free methoxide, in some cases by as much as 4600-fold. Overall the catalytic effects exhibited by the La 2 3+ system is spectacular for such substrates as paraoxon, where as little as 2 mmol L 1 La(OTf) 3 in the presence of equimolar NaOCH 3 accelerates the methanolysis by 10 9 -fold relative to the background reaction at neutral pH and ambient temperature.Key words: kinetics of methanolysis, metal ion catalysis, lanthanides, methanolysis of carboxylate esters and phosphate esters.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".