Chalcogenation of the 1,4-C<sub>2</sub>P<sub>4</sub> Ring: Oxidation, Isomerization, Insertion, and Ring Contraction
Bibliographic record
Abstract
The reaction of H2C(PCl2)2 with 4 equiv of (t)BuMgCl in tetrahydrofuran (THF) produces 1,4-(CH2)2(P(t)Bu)4, 1, in about 65% yield. This six-membered ring reacts directly with elemental sulfur or selenium in toluene at low temperatures to give the mono- and dichalcogenides 1,4-(CH2)2(P(t)BuE)(P(t)Bu)3 (E = S, 2a, E = Se, 2b) and 1,4-(CH2)2-2,5-(P(t)BuE)2(P(t)Bu)2 (E = S, 3a, E = Se, 3b). X-ray structural determinations showed that 3a and 3b are isostructural in the solid state; the six-membered C2P4 ring exhibits a twist-boat geometry with chalcogen substituents in syn positions in each case. Density functional theory (DFT) calculations for the three possible isomers of disubstitution were performed to elucidate the factors that favor the 2,5-isomer. Thermal isomerism was observed in solutions of 3b or 3a in toluene at 60 and 95 °C, respectively, to give the corresponding 2,6-isomers. With an excess of chalcogen in toluene at reflux, the four-membered rings (H2C)(P(t)BuE)2E (E = S, 4a, E = Se, 4b) were obtained and identified by multinuclear NMR spectroscopy and single crystal X-ray crystallography, which showed the (t)Bu groups in a trans orientation with respect to the CP2E ring. With a large excess of chalcogen, the five-membered rings (H2C)(P(t)BuE)2E2 (E = S, 5a, E = Se, 5b) were also observed; the X-ray structure of 5b revealed a half-envelope conformation for the CP2Se2 ring. The direct reaction of 4a with sulfur in boiling toluene does not produce 5a, whereas 5b is formed slowly and in low yields from 4b and selenium under similar conditions. On the basis of DFT calculations of the relative energies of likely intermediates, chalcogen insertion into the P-P bonds of 3a and 3b to give eight-membered C2P4E2 rings, followed by monomerization, is proposed as a feasible pathway for the formation of the four-membered CP2E heterocycles 4a and 4b.
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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) | 0.002 | 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 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".