Magnesium butadiene adduct:

The use of the second approach is restricted by the availability of 1,2-dimetallic derivatives of alkanes. The first example of a synthesis of 2-vinyl-substituted phosphiranes was described by Richter, using the magnesium-butadiene polymeric adduct (Equation (55)) <82AG(E)292, 83CB3293). A second example concerning the synthesis of phospha[3]radialenes has also been disclosed (Equation (56)) <91CB933>. The allenyl-substituted phosphiranes isomerise into phospha[3]radialenes upon distillation at standard pressure. 

A re-investigation of the Diels-Alder addition of butadiene to (-)-carvone has led to a reassignment of the structures of the major adduct (126) and the minor adduct (127).216 The isolation of the diol (128) on treating the ketone (129) with methyl-magnesium iodide is the result of a [2,3] sigmatropic rearrangement to (130) 217 this rearrangement may find application in artemisyl synthesis. 

Z)-2-Methoxy-l-(phenylthio)-l,3-butadienes react with methyl vinyl ketone and with 2-cyclohexen-1-one under catdysis by magnesium bromide or ethylaluminum dichloride. This provides exclusively the C 0 endo adducts in which the regiochemistry is completely controlled by the sulfur substituent despite the juxtaposed influence of the OMe group, e.g. (143) (144) (Scheme 36). ... 

The magnesium bromide catalyzed cycloaddition of (7 )-menthyl glyoxalate (la) to 1-trimethyl-siloxy-1,3-butadiene (2) gives adducts in 14% yield and a d.r. 54,5 45.5 (for 3), (f )-8-Phenyl-menthyl glyoxalate (lb), under identical conditions, produces adducts with a d.r. 91 9 (for 3) but with only 5% yield32. 

---