Synthesis of conjugated alkadienes

Miyaura, N. Yamada, K. Suginome, H. Suzuki, A. Novel and convenient method for the stereo- and regiospecific synthesis of conjugated alkadienes and alkenynes via the Pd-catalyzed cross-coupling reaction of 1-alkenyl-boranes with bromoalkenes and bromoalk-ynesj. Am. Chem. Soc. 1985, 107, 972-980. 

Most recently, a new and general synthesis of conjugated alkadienes has been reported by the reaction of 1-alkenyldiorgarioboranes with 1-alkenyl halides in the presence of palladium catalysts and bases 142). According to this procedure, (Z, E)-alkadienes are readily obtained, as revealed in Eq, 84. 

Reaction with Vinylic Halide. Synthesis of Conjugated Alkadienes... 

The stereo- and regioselective synthesis of conjugated alkadienes are of great importance in organic chemistry. A number of methods for the preparation of conjugated dienes and polyenes were developed uitilizing... 

Reductive elimination. A method for the synthesis of conjugated dienes and trienes involves reaction of l,4-dibenzoyloxy-2-alkenes and l,6-dibenzoyloxy-2,4-alkadienes with Na-Hg. 

It has been established that the course of the sequential pericyclic reaction of cyclopentadienones with acyclic conjugated alkadienes depends on the reaction temperature, thermal treatment at low temperatures affording 3a,4,7,7a-tetrahydroinden-l-one derivatives by way of a Cope rearrangement (see Scheme 38). Roman et al have developed an efficient stereoselective synthesis of enantiomerically pure i-nitrotricyclo[5.2.2.0 ]undeca-3,8-dienes via a tandem consecutive asymmetric Diels-Alder-Cope rearrangement (see Scheme 39). Adducts... 

For obtaining rearranged conjugated trienes 52a-e and 53a-e on a preparative scale, the reaction mixture from the synthesis in 1 -(2, 6, 6 -trimelhyl-1 -cyclohexen-l -yl)-3-(phenylsulfinyl)-1,2-alkadienes 51a-c (200-300 mg) (both diastereomers of the vinylallene sulfoxides) after Et20 workup is allowed to stand in Et20 (15-20 mL) at r.t. for > lOh. The residue after removal of solvent is subjected to 1IPLC purification (Whatman Partisil M 9 10/50 column, 10-20% ElOAc/Skellysolve B) to afford the two conjugated trienes. From 51a yield 63% ratio (53a/52a) 81 19 from 51 b yield 91 % ratio (53b/52b) 92 8 from 51c yield 75% ratio (53c/52c) 92 8 from 51 d yield 80% ratio (53d/52d) 94 6 from 51e yield 58% ratio (53d/52d) >98 2,... 

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