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Danishefsky’s diene

Danishefsky’s diene (Kitahara diene) is an organic compound and a diene with the formal name trans-1-methoxy-3-trimethylsilyloxy-l,3-butadiene^[1]. Because the diene is very electron-rich it is used as a very reactive reagent in Diels-Alder reactions. The OMe group allows for the Diels-Alder reaction to be made regiospecific, since the electrophilic carbon to which it is attached will react preferentially with the most nucleophilic atom of a dienophile.

Its first reported synthesis was by reaction of trimethylsilyl chloride with 4-methoxy-3-buten-2-one and zinc chloride ^[2] :

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Its reaction with maleic anhydride is a fast one.

In a reaction with an alkene the silyl ether is a synthon for a carbonyl group through an enol while the ether group is susceptible to an elimination reaction and capable of forming a new alkene group. In addition 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 ^[3] ^[4]:

References

^ Danishefsky, S.; Kitahara, T. Useful diene for the Diels-Alder reaction. J. Am. Chem. Soc. 1974, 96, 7807-7808. doi:10.1021/ja00832a031
^ Preparation and Diels-Alder Reaction of a Highly Nuclerophilic Diene. Org. Synth., Coll. Vol. 7, p.312 (1990); Vol. 61, p.147 (1983). Link
^ Asymmetric aza-Diels-Alder reaction of Danishefsky's diene with imines in a chiral reaction medium Pegot B, Nguyen Van Buu O, Gori D, Vo-Thanh G Beilstein Journal of Organic Chemistry, 2006 Link
^ This is an asymmetric reaction with a chiral ionic liquid as chiral solvent. The reported chemical yield is 66% with 60% diastereomeric excess