Allylic barium reagents allylation reactions using

Homo- and cross-coupling reactions of allyhc halides and reactions of conjugated dienes with dichloroalkanes using reactive barium are reviewed in Section 5.2. The next section covers methods of generating allylic barium reagents and reactions of these carbanions with a variety of electrophiles. The last section describes examples of other carbon-carbon bond forming reactions promoted by barium compounds. 

Scheme 10.1 Various allylation reactions using allylic barium reagents.

Allylic barium reagents prepared in this way can realize highly a-selective reactions with different electrophiles, e.g. cross-coupling reactions with allylic halides or allylic phosphates, additions to carbonyl compounds or imines, and ring opening of epoxides. A selective Michael addition reaction with an a,/ -unsaturated cy-cloalkanone can also be performed by use of an allylic barium reagent. 

Allylation. Active barium is generated by reduction of Bah with 2 equivalents of Li biphenylide in THF at room temperature. Allylic chlorides are converted to the allylbarium reagents, which can be used to effect allylation with excellent regio- and stereoselectivities. r/ireo-Homoallylic alcohols from a y-selective reaction with aldehydes are obtained. ... 

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