4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE
Synonym(s):4-Phenyl-3,5-dihydro-4H-1,2,4-triazole-3,5-dione, PTAD;4-Phenyl-3H-1,2,4-triazole-3,5(4H)-dione;Cookson reagent;PTAD
- CAS NO.:4233-33-4
- Empirical Formula: C8H5N3O2
- Molecular Weight: 175.14
- MDL number: MFCD00003148
- EINECS: 224-191-7
- SAFETY DATA SHEET (SDS)
- Update Date: 2026-01-13 11:20:04
What is 4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE?
Chemical properties
4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE is Red Solid
The Uses of 4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE
4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE is used in the methods for determining levels of 1,25 dihydroxyvitamin d2 and d3 in biological and food samples and dietary supplements.
The Uses of 4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE
4-Phenyl-1,2,4-triazoline-3,5-dione (PTAD) can be used as an efficient and selective reagent for the oxidation of thiols to disulfides.
It can also be used:???????
- As a dehydrogenating agent to synthesize annulated dihydropyridazines by inverse [4+2] cycloaddition reaction between cyclic alkenes and 1,2,4,5-tetrazines.???????
- As a dienophile to synthesize cycloaddition products by fast hetero-Diels?Alder reactions.???????
- As an efficient oxidizing agent for the synthesis of pyridine derivatives from 1,4-dihydropyridines.
- In the synthesis of urazoles via [3+2] cycloaddition with allylsilanes.
The Uses of 4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE
4-Phenyl-1,2,4-triazoline-3,5-dione may be used as a derivatizing reagent for the determination of trace levels of 25-hydroxyvitamin D and its C-3 epimer in biological samples and cholecalciferol (vitamin D3) in fortified infant formula, milk and milk powder using liquid chromatography–tandem mass spectrometry (LC–MS/MS)technique.
Synthesis Reference(s)
Synthetic Communications, 17, p. 409, 1987 DOI: 10.1080/00397918708063918
General Description
4-Phenyl-1,2,4-triazoline-3,5-dione, also known as Cookson reagent, is a strong dienophile, which gives a stable Diels-Alder adduct quantitatively within a short time and under mild conditions. It is commonly used as a protecting group of the diene moiety for the synthesis of vitamin D3 (VD3)-related compounds.
Purification Methods
PTAD forms carmine red needles by sublimation (ice cold finger) at 100o/0.1mm, and/or by recrystallisation from EtOH. IR: 1760 and 1780 cm-1 . [Cookson et al. Org Synth 51 121 1971, Moore max et al. J Org Chem 39 3700 1974, Beilstein 26 I 57, 26 III/IV 540.]
Properties of 4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE
| Melting point: | 165-170 °C (dec.)(lit.) |
| Boiling point: | 263.8±23.0 °C(Predicted) |
| Density | 1.47±0.1 g/cm3(Predicted) |
| storage temp. | 2-8°C |
| solubility | Chloroform (Sparingly), DMSO (Slightly), Ethyl Acetate (Slightly), Methanol (Sli |
| form | Solid |
| pka | -1.71±0.20(Predicted) |
| color | Red to Dark Red |
| BRN | 141548 |
| CAS DataBase Reference | 4233-33-4(CAS DataBase Reference) |
Safety information for 4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE
| Signal word | Warning |
| Pictogram(s) |
![]() Exclamation Mark Irritant GHS07 |
| GHS Hazard Statements |
H302:Acute toxicity,oral |
| Precautionary Statement Codes |
P280:Wear protective gloves/protective clothing/eye protection/face protection. P305+P351+P338:IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing. |
Computed Descriptors for 4-PHENYL-1,2,4-TRIAZOLINE-3,5-DIONE
| InChIKey | ISULLEUFOQSBGY-UHFFFAOYSA-N |
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