Assisted hydrolysis of <i>cis</i>-2-(3-phenylthioureido)cyclo pentane-carbonitrile in alkaline solution. Solvent dependent switch from hydrolysis to rearrangement of the iminothiooxopyrimidine intermediate
Bibliographic record
Abstract
The cis and trans isomers of 2-(3-phenylthioureido)cyclopentanecarbonitrile, 1, and the respective carboxamides, 3, and acids, 4, have been prepared. Acid cyclization of both nitriles, faster with the cis isomer, gave the more stable cis-2-thiooxo-cyclopenta[d]pyrimidin-4-one, 7. In base cis-1 formed the cis 4-imino-2-thiooxopyrimidine 2 which in aqueous alkali broke down via 3 to the acid 4; while in the presence of 66% acetonitrile 2 rearranged to the 4-phenyliminopyrimidine 5 to give as final product the thioureido acid 6 carrying no phenyl group. The 1H NMR data for imino and phenylimino derivatives 2 and 5 showed strong bias for conformation A with 1-N pseudoaxial in the cyclopentane ring. Spectra of the E andZ isomers of the iminopyrimidine 2 under slow exchange could be recorded in DMSO-d6. The phenylimino tautomer of 5 is observed in CD3OD and in CDCl3 with the E and Z isomers in a 1:1 ratio. In DMSO-d6 the phenylamino tautomer 5a is also detected. The first process in aqueous KOH, the conversion of nitrile cis-1 into the imino intermediate 2, reaches an equilibrium which shifts towards the nitrile at higher alkalinities because of ionization of the phenylthioureido group (Ke = [2]/[1] = 2.43 and pKAH = 12.74). The cyclization of 1 to 2 is first order in [OH-] while the slower breakdown of 2 is pH independent. The latter is 104 times faster than the hydrolysis of acetonitrile evidencing substantial anchimeric assistance. The change in the reaction route towards the rearranged phenyliminopyrimidine 5 upon addition of acetonitrile can be caused by the lower dielectric constant favouring the elimination step leading to the intermediate isothiocyanate, and by increased activity of OH- accelerating the (presumably) second order elimination step as opposed to the pH-independent hydrolysis of the imino derivative 2. Key words: anchimeric assistance, phenylthioureido nitriles, iminothiooxopyrimidine tautomers, alkaline hydrolysis, solvent effects.
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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) | 0.000 | 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 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".