| Danishefsky's diene[1] | |
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Other names
Kitahara diene |
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| Identifiers | |
| CAS number | 54125-02-9 |
| PubChem | 5366448 |
| ChemSpider | 4518295 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C8H16O2Si |
| Molar mass | 172.3 g mol−1 |
| Exact mass | 172.091956289 g mol–1 |
| Density | 0.89 g cm–3 (20 °C)[2] |
| Boiling point |
68-69 °C, 341-342 K, 154-156 °F (at 0.0189 kPa[2]) |
| Hazards | |
| R-phrases | - |
| S-phrases | S23, S24/25 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Danishefsky’s diene (Kitahara diene) is an organosilicon compound and a diene with the formal name trans-1-methoxy-3-trimethylsilyloxy-1,3-butadiene named after Samuel J. Danishefsky.[3] Because the diene is very electron-rich it is a very reactive reagent in Diels-Alder reactions. This diene reacts rapidly with electrophilic alkenes, such as maleic anhydride. The OMe group promotes highly regioselective additions.
It was first synthesized by the reaction of trimethylsilyl chloride with 4-methoxy-3-buten-2-one and zinc chloride:[4]
The diene has two features of interest: the substituents promote regiospecific addition to unsymmetrical dienophiles and the resulting adduct is amenable to further functional group manipulations after the addition reaction. High regioselectivity is obtained with unsymmetrical alkenes with a preference for an 1,2-relation of the ether group with the electron-deficient alkene-carbon. All this is exemplified in this Aza Diels-Alder reaction:[5][6]
In the cycloaddition product, the silyl ether is a synthon for a carbonyl group via the enol. The methoxy group is susceptible to an elimination reaction enabling the formation of a new alkene group.