Chapter 18, Problem 42P

Interpretation Introduction

Interpretation:

The short sequences of reactions that would be appropriate for the given transformations, using the indicated starting material are to be written.

Concept introduction:

Friedel Craft acylation is an electrophilic aromatic substitution reaction. In this reaction synthesis of mono acylated product takes place from the reaction between aromatic rings and acyl chlorides.

Grignard reaction is a reaction in which aryl or alkyl magnesium halides react with carbonyl compounds to produce an alcohol with the addition of the alkyl substituent to the carbonyl carbon.

The molecule, ${\text{H}}_{\text{2}}$ in presence of metal catalyst, $\text{Pd}/\text{C}$ acts as a reducing agent.

Dess Martin periodinane (DMP) is a reagent which is used for the oxidation of primary alcohols to aldehydes and secondary alcohols to ketones.

The Diels–Alder reaction is a chemical reaction between to form a substituted cyclohexene derivative as product from the reaction between a conjugated diene and a substituted alkene.

Answer to Problem 42P

Solution:

a) Short sequences of reactions that are appropriate for the transformation of $5,5-$ dimethylcyclononanone to $1,1,5-$ Trimethylcyclononane are given below.

b) Short sequences of reactions for the transformation of the given compounds are shown below.

c) Short sequences of reactions for the transformation of the given compound from $o-$ Bromotoluene and $5-$ hexenal are shown below.

d) Short sequences of reactions for the transformation of the given compounds are shown below.

e) Short sequences of reactions that are appropriate for the transformation of the given compound from $\text{3-}$ Chloro $-2-$ methylbenzaldehye are shown below.

f) Short sequences of reactions that are appropriate for the transformation of the given compounds are shown below.

g) Short sequences of reactions that are appropriate for the transformation of the given compounds are shown below.

Explanation of Solution

a) Short sequences of reactions that would be appropriate for the transformation of $5,5-$ dimethylcyclononanone to $1,1,5-$ Trimethylcyclononane have to be decribed.

Treatment of $5,5-$ dimethylcyclononanone with griginard reagent ${\text{CH}}_{\text{3}}\text{MgBr}$ followed by its hydrolysis produces a tertiary alcohol as shown in the reaction below.

The tertiary alcohol so obtained undergoes dehydration with conc. ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ and results in the formation of an alkene as shown below.

Reduction of the alkene with ${\text{H}}_{\text{2}}$ in presence of metal catalyst, $\text{Pd}/\text{C}$ produces $1,1,5-$ Trimethylcyclononane as shown below.

b) Short sequences of reactions that would be appropriate for the transformation of the compounds given below have to be decribed.

Treatment of cyclopentyl(phenyl) methanone with griginard reagent ${\text{CH}}_{\text{3}}\text{MgBr}$ followed by its hydrolysis produces a tertiary alcohol as shown in the reaction below.

The tertiary alcohol, upon dehydration with conc. ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ results in the formation of ($1-$ cyclopentylidene (ethyl) benzene as shown below.

c) The structure of the compound which has to be synthesized from $o-$ Bromotoluene and $5-$ hexenal is shown below.

The reaction of $o-$ Bromotoluene with $\text{Mg}$ in the presence of dry ether results in the formation of griginard reagent as shown below.

The griginard reagent formed reacts with $5-$ hexenal to form alcohol as shown below.

The alcohol formed reacts with dess martin periodinane to form ketone as shown in the reaction below.

The ketone reacts with Wittig reagent ${\text{H}}_{\text{2}}{\text{C=PPh}}_{\text{3}}$ to give the desired product.

d) Short sequences of reactions that would be appropriate for the transformation of the compounds given below have to be described.

Oxidation of the given alcohol using pyridinium dichromate (PDC) in ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ converts the primary alcohol to an aldehyde as shown below.

Protection of acidic proton of is done by reaction of the aldehyde with ${\left({\text{CH}}_{\text{3}}\right)}_{\text{3}}\text{SiCl}$ in presence of pyridine as shown below.

Reaction of the aldehyde with the griginard reagent, hexylmagnesium chloride, produces an alcohol as shown in the reaction below.

Alcohols react with martin dess periodinane to form ketone as shown below.

Terminal alkynes are converted to ketones by reaction with ${\text{HgSO}}_{\text{4}}$ Iin the presence of ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ as shown below to give the desired product.

e) The structure of the compound which has to be synthesized from $\text{3-}$ Chloro $-2-$ methylbenzaldehye is shown below.

In the reduction of $\text{3-}$ Chloro $-2-$ methylbenzaldehye by lithium aluminum hydride (LAH) followed by hydrolysis, the aldehydic group is reduced to primary alcohol as shown below.

The hydroxyl group of the alcohol is a poor leaving group and therefore, it is reacted with $\text{TsOCl}$ to convert it into a good leaving group as shown in the reaction below.

The $\text{OTs}$ group in the above reaction is substituted with $-{\text{OCH}}_{\text{3}}$ by reaction with sodium methoxide, ${\text{CH}}_{\text{3}}\text{ONa}$ as shown in the reaction below.

f) Short sequences of reactions that would be appropriate for the transformation of the compounds given below have to be decribed.

Reduction of the ketone shown above with zinc-amalgam produces a hydrocarbon in Clemmenson’s reduction as shown in the reaction below.

Friedal Crafts acylation of the aromatic ring obtained with ${\text{CH}}_{\text{3}}\text{COCl}$ in the presence of Lewis acid catalyst ${\text{AlCl}}_{\text{3}}$ produces the desired product as shown in the reaction below.

g) Short sequences of reactions that would be appropriate for the transformation of the compounds given below have to be decribed.

Treatment of the reactant with griginard reagent ${\text{CH}}_{\text{3}}\text{MgBr}$ followed by its hydrolysis produces a tertiary alcohol as shown in the reaction below.

The tertiary alcohol so obtained undergoes dehydration with conc. ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ and results in the formation of an alkene as shown below.

Diels-Alder reaction of the diene with the dienophile produces the desired product as shown in the reaction below.