Reactions of Et(3)ZnLi with ketones: electronic and steric effects(1)

Toluene solutions of composition Et(3)ZnLi react rapidly with aldehydes and ketones to form addition products. Et(3)ZnNa and Et(3)ZnK solutions react readily with the same substrates although metalation, as well as addition, is significant with substrates having alpha-hydrogens. The Et(3)ZnM solutions react with 2-cyclohexenone to give mainly the 1,4-addition product. Relative rates of addition of Et(3)ZnLi to substituted acetophenones give a Hammett rho of 2.78. Addition of Et(3)ZnLi to acetophenone is slowed significantly by alpha and ortho methyl substituents; relative rates of addition to acetophenone, o-methylacetophenone, and tert-butyl phenyl ketone are 1.00, 0.012, and 0.003.