Transition metal enolates unsymmetrical ketones

An enolate formed from an unsymmetric ketone can be of two types the less electronegative (usually more substituted) side is deprotonated preferentially by many homogeneous transition metal complexes with N-donor or halide ligands, " in agreement with local hard-soft acid-base concepts. But steric hindrance plays a greater role with heterogeneous catalysts, to such an extent that the less substituted side is often deprotonated preferentially. ... 

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