Reactions with allyl metal compounds

For earlier reviews of the reactions of allyl metal compounds with aldehydes and imines, see (a) Y. 

Oligomerization of olefins or acetylenes can also occur in their reactions with transition metal compounds. Treatment of rutheniimi trichloride in 2-methoxyethanol with butadiene at 90°C yields the complex 6.7 the structure of which has been determined by X-ray diffraction. (Related reactions involving bis-ir-allyl nickel and butadiene arc discussed in Chapter 10.)... 

Allylic metal compounds useful for further transformations can be prepared by Pd-catalyzed reactions of allylic compounds with bimetallic reagents. By this transformation, umpolung of nucleophilic 7r-allylpalladium complexes to electrophilic allylmetal species can be accomplished. Transfer of an allyl moiety from Pd to Sn is a typical umpolung. 

Higher 43-hydrocarbyl derivatives of transition metals can be obtained by partial protolysis of the bis(7i-allyl)metal compounds formed from cyclo-octa-1,5-diene metal complexes and 1,3-butadiene with one equivalent of the Bronsted acid in the presence of the proper ligand in a polar solvent at lowered temperature (e.g. — 40°C). For instance, Ni [43-(CxHn)l and Ni—[43-(Ci2Hig)] derivatives have been yielded by the reaction of Ni(CxH 2)2 [(Ni(Cod)2] with 1,3-butadiene (C4H6), followed by treatment with a Bronsted acid, according to scheme (1) [132] and scheme (2) [37] respectively ... 

The class of ene reactions with carbonyl compounds as the enophile, which we denote the carbonyl-ene reaction [45], is an efficient alternative to the carbonyl addition reaction of allylic metals (Sch. 11). 

There are two main synthetic applications where the reaction of an allyl system with electrophiles is accompanied by an allylic rearrangement. One consists of the use of heteroatom-substituted allylic anions as homoenolate anion equivalents and the other represents a synthetically valuable alternative to the aldol reaction by addition of allyl metal compounds to aldehydes. 

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