Stereospecific reduction and cross-coupling of .gamma.-monosubstituted allylic chlorides using coordinatively unsaturated palladium catalysts

In stereospecific reduction of (E)- and (Z)-γ-monosubstituted allylic chlorides has been accomplished via low-temperature hydride capture of the corresponding π-allylpalladium complexes. In addition, cross-coupling of a (Z)-γ-monosubstituted allylic chloride with an organometallic reagent has been achieved without loss of double bond geometry. Key to these processes is the use of reactive, coordinatively unsaturated palladium species which promote C-H and C-C bond forming reactions prior to isomerization of the allylic double bond. Although the latter process furnishes predominantly «head to head» coupled products, formation of regioisomers remains a problem