Reversible decomposition of mono(α-hydroxy)phosphines and their reaction with α,β-unsaturated aldehydes
Bibliographic record
Abstract
The mono(α-hydroxy)phosphines R 2 PCH(OH)R′ (R = Ph, R′ = H, Et, CH 2 Ph, Ph, p-X-C 6 H 4 ; R = cyclohexyl, R′ = Ph) are prepared under solvent-free conditions by a 1:1 reaction of Ph 2 PH with the appropriate aldehyde, and their stabilities (with respect to reversible dissociation into reactants), studied in DMSO, Et 2 O, and MeOH, increase with decreased basicity of the hydroxyphosphine; for example, for the Ph 2 PCH(OH)C 6 H 4 -p-X phosphines, stability decreases in the order: X = CN > Cl > F > H > Me > OMe. A 1:1 room-temperature reaction of the (α-hydroxy)phosphines (except for R′ = H) with cinnamaldehyde in DMSO slowly yields the known mono- and di-phosphines Ph 2 PCH(Ph)CH 2 CHO (4a) and Ph 2 PCH(Ph)CH 2 CH(PPh 2 )OH (10a), and the corresponding R′CHO aldehyde. In MeOH, the sequentially formed intermediates, PhCH=CHCH(OH)PPh 2 , PhCH(OH)CH=CHPPh 2 , and Ph 2 PCH(Ph)CH=CHOH, were detected en route to 4a and 10a. Reaction of cinnamaldehyde with Ph 2 PCH 2 OH gives 4a and the hemiacetal Ph 2 PCH 2 OCH 2 OH formed from the reactant hydroxyphosphine with the co-product formaldehyde. Reactions carried out in MeOH are faster because of the formation of hemiacetals from the phosphine-containing aldehyde products; thus, 4a is seen as Ph 2 PCH(Ph)CH 2 CH(OMe)(OH), which on dissolution in Et 2 O, reverts to the aldehyde. The reaction rates and equilibrium concentrations of the various species depend on the R′ group of the reactant phosphine; the rates of consumption of the hydroxyphosphines in the reactions with cinnamaldehyde decrease in the order: Ph 2 PCH(OH)Ph > Ph 2 PCH(OH)Et > Ph 2 PCH(OH)CH 2 Ph >> Ph 2 PCH 2 OH. The reactivity pattern of Ph 2 PCH(OH)Ph with sinapaldehyde [3,5-(OMe) 2 -4-OH-cinnamaldehyde] in DMSO follows that seen for cinnamaldehyde. Reaction of Ph 2 PH with cinnamaldehyde in DMSO affords 4a and 10a via the same intermediates seen with the Ph 2 PCH(OH)R′ reagents, but these latter reactions are thought to occur via direct attack on cinnamaldehyde by the hydroxyphosphine rather than via Ph 2 PH.
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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) | 0.001 | 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".