C−H Activation with Elemental Sulfur: Synthesis of Cyclic Thioureas from Formaldehyde Aminals and S8
Why this work is in the frame
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Bibliographic record
Abstract
The C-H activation of cyclic formaldehyde aminals LCH2 (L = RN-CH2CH2CH2-NR and RNCH2CH2-NR, R = Me, Et, iPr, tBu, or Ph) with S8 proceeds at unusually low temperatures (T< 160 degrees C) and results in the formation of the respective thioureas LC=S and H2S. The reaction constitutes a new, solvent-free method for the synthesis of thioureas that eliminates the toxic and highly flammable CS2. For R = tBu, the ionic carbenium thiocyanates [LCH]+ SCN- dominate the product spectrum and the respective thioureas are obtained in low yield. The reactivity of the analogous sulfur and oxygen ring systems towards S8 was investigated. 1,3-Dithiolane is cleanly converted into 1,3-dithiolane-2-thione (S8, 14 d, 190 degrees C) and resembles the cyclic formaldehyde aminals in this respect. 1,3-Dioxolane (L = OCH2CH2O) is completely inert towards sulfur even under forceful reaction conditions (190 degrees C, 14 d). The formation of thioureas from aminals was investigated at the CBS-4 and B3LYP/6-31G(d) levels of theory.
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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) | 0.001 | 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 it