Competing photodehydration and excited-state intramolecular proton transfer (ESIPT) in adamantyl derivatives of 2-phenylphenols
Bibliographic record
Abstract
2-Phenylphenol derivatives strategically substituted with a hydroxyadamantyl substituent were synthesized and their photochemical reactivity was investigated. Derivatives 9 and 10 undergo competitive excited-state intramolecular proton transfer (ESIPT) from the phenol to the carbon atom of the adjacent phenyl ring and formal ESPT from the phenol to the hydroxyl group coupled with dehydration. These two processes (both via S 1 ) give rise to two classes of quinone methides (QMs) that revert to starting material or react with nucleophiles, respectively. ESIPT to carbon atoms was studied by performing photolyses in the presence of D 2 O, whereupon deuterium incorporation to the adjacent phenyl ring was observed ([Formula: see text] = 0.1–0.2). The competing formal ESPT and dehydration takes place with quantum yields that are an order of magnitude lower and was studied by isolation of photomethanolysis products. Derivative 8 did not undergo ESIPT to carbon atom. Owing to the presence of an intramolecular H bond, an efficient ESIPT from the phenol to the hydroxyl group coupled with dehydration gives a QM that efficiently undergoes electrocyclization (overall [Formula: see text] = 0.33), to give chroman 16. In addition, spiro[adamantane-2,9′-(4′-hydroxy)fluorene] (12) undergoes ESIPT, unlike the previously reported unreactive parent 2-hydroxyfluorene. The reactive singlet excited states of the prepared biphenyl and fluorene molecules were characterized by fluorescence spectroscopy, whereas laser flash photolysis (LFP) was performed to characterize the longer lived QM intermediates.
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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) | 0.000 | 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) | 0.000 | 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".