Synthesis of substituted phenols by directed <i>ortho</i>-lithiation of in situ <i>N</i>-silyl-protected <i>O</i>-aryl <i>N</i>-monoalkylcarbamates
Bibliographic record
Abstract
A simple, high-yield procedure has been developed for the ortho-lithiation and subsequent ortho-substitution of phenols by a manifold of electrophiles. N,C-Dilithiation of O-aryl N-monoalkylcarbamates proved to be impossible due to a cleavage reaction of the monolithiated intermediates. However, in situ N-silylation of O-aryl N-isopropylcarbamates proceeds smoothly with trialkylsilyl triflates N,N,N',N'-tetramethylethylenediamine (TMEDA). Separation of the formed O-aryl N-isopropyl-N-trialkylsilylcarbamates from the byproduct TMEDA·HOTf, which is insoluble in diethyl ether or toluene, is not required. ortho-Lithiation with n-butyllithiumTMEDA at 78°C leads to the corresponding aryllithium, which does not undergo anionic ortho-Fries rearrangement under the reaction conditions, but is efficiently substituted by electrophilic reagents. During the aqueous work-up, the N-silyl group is removed and the corresponding ortho-substituted O-aryl N-isopropylcarbamate is isolated. Among the introduced electrophiles are: Me 3 Si, Bu 3 Sn, PhS, I, Br, Cl, alkyl, α-hydroxyalkyl. Liberation of the free phenols is performed under mild alkaline conditions.Key words: directed ortho-metalation, ortho-lithiated O-aryl carbamates, ortho-substituted phenols, in situ protection of N-monoalkylcarbamates.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.002 | 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".