Titanium Tetraisopropoxide Promoted Reactions for the Synthesis of Substituted Coumarins
Bibliographic record
Abstract
Substituted coumarins are synthesized by the reaction of salicylaldehyde derivatives with malonitrile, isopropyl cyanoacetate or diisopropyl malonate promoted by Ti(O-i-Pr) 4 .When i-PrOH is used as a solvent, these reactions proceeded by the catalytic amount of Ti(O-i-Pr) 4 (~0.1 equivalent).The coumarin moiety exists widely such as in perfume compounds, dye compounds, and pharmaceutical agents. 1,2Furthermore, coumarin derivatives have utilities in a wide range of scientific fields.For example, the coumarins are known as fluorescent probe molecules for measurements of solvation dynamics. 3Therefore, several synthetic methods of the functionalized coumarins have been developed.There are fundamentally two methods, one is the so-called Pechmann condensation, that is, acid-mediated condensation of phenol with -ketoesters to produce coumarins. 4In these reactions, strong acids such as H 2 SO 4 and AlCl 3 have been used.The other methods for synthesis of the coumarins is the reaction of salicylaldehydes (o-hydroxybenzaldehydes) with the active methylene compounds via Brønsted base-promoted Knoevenagel 5 reaction and following Brønsted acid-promoted intramolecular Pinner reaction. 6 During the course of our mechanistic study for the enantioselective reaction between aldehydes and diketene catalyzed by the chiral Schiff base __ Ti(O-i-Pr) 4 complex, 7 we observed the Knoevenagel reaction promoted by Ti(O-i-Pr) 4 at room temperature. 8Then, we reported an Knoevenagel reaction of aldehydes or ketones with malononitrile, isopropyl cyanoacetate and diisopropyl malonate catalyzed by Ti(O-i-Pr) 4 in i-PrOH as a solvent. 9When i-PrOH was used as a solvent, the Knoevenagel reaction proceeded by the only catalytic amount of Ti(O-i-Pr) 4 (~5 mol%).In this paper, we will describe the ------
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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) | 0.001 | 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".