Page 243 - Advanced Organic Chemistry Part B - Reactions & Synthesis

3

Functional Group

Interconversion

by Substitution, Including

Protection and Deprotection

Introduction

Chapters 1 and 2 dealt with formation of new carbon-carbon bonds by reactions in
which one carbon acts as the nucleophile and another as the electrophile. In this
chapter we turn our attention to noncarbon nucleophiles. Nucleophilic substitution is
used in a variety of interconversions of functional groups. We discuss substitution
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at both sp carbon and carbonyl groups. Substitution at saturated carbon usually
involves the S 2 mechanism, whereas substitution at carbonyl groups usually occurs
N
by addition-elimination.

Substitution at saturated carbons

R C X + Nu: – Nu C R + X –
Substitution at carbonyl groups
O O – O
C + Nu: – R C X C + X –
R X Nu R Nu

The mechanistic aspects of nucleophilic substitutions at saturated carbon and carbonyl
centers were considered in Part A, Chapters 4 and 7, respectively. In this chapter we
discuss some of the important synthetic transformations that involve these types of
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