Allylbarium reagents

Allylbarium reagents homoallylic alcohols. The reaction of anhydrous Bal2 with lithium biphenylide (2 cquiv.) in THF provides a reactive barium species that reacts with allylic chlorides at —78° to form allylbarium chlorides. These reagents react with high a-selcctivity with carbonyl compounds to form homoallylic alcohols with retention of configuration. 

Organobarium reagents. 17. 204-21 Allylation. Active barium is gei of Li biphenylide in THF at room tern allylbarium reagents, which can be us stereoselectivities. rlireo-Homoallylie hydes are obtained. ... 

Dienes. The coupling of allylbarium reagents with allylic bis-12.2,2-trifluoroethyl)phosphates proceeds at a and a positions and is thus different from that of Grignard reagents (a,y cross coupling). Hence, little transposition occurs with the use of the allylic phosphate esters in these reactions. 

P,y-Unsatunaed carboxylic acids. Carboxylation of allylbarium reagents, generated in situ, proceeds with high a-selectivity. Note that carboxylation of allylmagnesium proceeds with high y-selectivity. 

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