Danishefsky's diene

• Trans-1- methoxy-3- trimethylsilyloxy -1 ,3-butadiene
• (E )-1- methoxy-3- trimethylsilyloxy -1 ,3-butadiene

Colorless liquid

Liquid

0.89 g · cm -3 ( 20 ° C)

68-69 ° C ( 18.9 hPa)

Attention

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The Danishefsky diene (after Samuel Danishefsky ) is a chemical compound from the class of dienes. It has the basic structure of 1,3-butadiene, having a trimethylsilyl ether in the 1-position and a methoxy group in the 3-position.

Properties

It is a colorless liquid having a refractive index of 1.454 (20 ° C). The flash point is 59 ° C.

Production

The Danishefsky diene can be synthesized from commercially available trans-4- methoxybut -3 -en- 2-one. This is first deprotonated with a base, for example triethylamine. The resulting enolate is stabilized with zinc chloride and reacted with chlorotrimethylsilane to Danishefsky's diene.

Use

The Danishefsky diene is used for the Diels- Alder reaction. It allows for the synthesis of products with a carbonyl in a position that is not accessible with other dienes in a Diels- Alder reaction. This is controlled by the work-up: After the Diels -Alder reaction of the silyl ethers can be cleaved with dilute hydrochloric acid, which initially results in an enol, which then tautomerization to ketone. The resulting ketone may be a useful functionalization to the following reaction steps. The methoxy group can be cleaved sour, if it is not desired, a double bond results.

The Danishefsky's diene is an electron-rich diene and shows reactions in a high regioselectivity. The most electron-rich position is located at C-1, to which the methoxy group is bound. Become an unsymmetrical dienophiles are used, this position preferably reacts with the electron-deficient position of the dienophile used. Even in hetero-Diels -Alder reactions, the Danishefsky diene can be used. One example is an aza Diels- Alder reaction, in which the C = N double bond of the imine act as a dienophile:

Variants

There are also variations of the Danishefsky diene. Here most other residues at the silyl ether and the ether are used. These are grouped under the collective term Danishefsky dienes.