Chapter 19, Problem 19.72P

Interpretation Introduction

(a)

Interpretation:

It is to be shown how to synthesize the given compound, using the given restrictions on the starting material.

Concept introduction:

The nucleophilic addition of the enolate anion to the $\text{α,β-}$ unsaturated carbonyl compound is known as conjugate addition or the Michael addition. This addition is reversible with respect to the carbonyl group so the carbonyl group is regenerated. Sodium borohydride (${\text{NaBH}}_{\text{4}}$) is good reducing and reduces aldehyde and ketone to corresponding primary and secondary alcohol respectively.

Interpretation Introduction

(b)

Interpretation:

It is to be shown how to synthesize the given compound, using the given restrictions on the starting material.

Concept introduction:

$\text{α,β-}$ unsaturated carbonyl compound on treatment with $\text{HCN}$ in catalytic amount of $\text{KCN}$ or $\text{NaCN}$ the nucleophile (${\text{CN}}^{\text{-}}$) adds to the $\text{β}$ carbon of the reactant, therefore this addition is nothing but $\text{1, 4-addition}$. This addition is reversible with respect to the carbonyl group so the carbonyl group is regenerated. LAH (${\text{LiAlH}}_{\text{4}}$) is a strong reducing agent which reduces nitrile group to corresponding primary amine group.

Interpretation Introduction

(c)

Interpretation:

It is to be shown how to synthesize the given compound, using the given restrictions on the starting material.

Concept introduction:

Aldehyde on treatment with $\text{HCN}$ in the catalytic amount of $\text{KCN}$ or $\text{NaCN}$ the corresponding cyanohydrin is formed. The protection of an alcoholic OH group is done by the treatment one of the protecting reagent, $\text{TBDMSCl}$. The protected form of the alcohol is stable under the basic condition and for deprotection, ${\text{F}}^{\text{-}}$ ion source is used. Nitrile on the treatment with Grignard reagent followed by an acid workup corresponding ketone is formed. Sodium borohydride (${\text{NaBH}}_{\text{4}}$) is good reducing and reduces aldehyde and ketone to corresponding primary and secondary alcohol respectively.

Interpretation Introduction

(d)

Interpretation:

It is to be shown how to synthesize the given compound, using the given restrictions on the starting material.

Concept introduction:

1, 5-deketo compound undergoes intramolecular Aldol reaction under the basic condition to form the cyclic corresponding cyclic β-hydroxy ketone as a product. Sodium borohydride (${\text{NaBH}}_{\text{4}}$) is good reducing and reduces aldehyde and ketone to corresponding primary and secondary alcohol respectively. An alcohol on treatment with ${\text{PBr}}_{\text{3}}$, the OH group of the alcohol is replaced by bromine atom via back to back ${\text{S}}_{\text{N}}\text{2}$ reaction.