A readily available and simple (MW = 444.5 g/mol) valine-based chiral phosphine is used to promote highly efficient catalytic asymmetricconjugate additions of dialkyl- and diarylzinc reagents to acyclic
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-silyl-
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,
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-unsaturated ketones. The catalytic asymmetric protocol allowsaccess to versatile allylsilanes that bear a trisubstituted olefin in high diastereo- and enantiomeric purity.