Chapter 17, Problem 17.63P

Interpretation Introduction

Interpretation:

The conjugate addition of ${\text{NaBH}}_{\text{4}}$ to an alpha, beta unsaturated carbonyl compound occurs to a small extent, but when it does, it results in two sequential nucleophilic additions. It is to be explained why the conjugate addition of a lithium dialkylcuprate (${\text{R}}_{\text{2}}\text{CuLi}$), on the other hand, results in only a single nucleophilic addition.

Concept introduction:

The weak resonance contributor with separated charges generates a small, partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon.