Chapter 26, Problem 26.48P

Interpretation Introduction

(a)

Interpretation: The product formed from the ring-closing metathesis of given compound is to be drawn, and the synthesis of metathesis starting material using ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$, alcohols with less than five carbons, and any needed organic and inorganic reagents is to be stated.

Concept introduction: The ring-closing metathesis (RCM) by Grubbs catalyst occurs, when the starting material is diene. This reaction is facilitated under high-dilution condition as it favors intramolecular metathesis instead of intermolecular metathesis.

Answer to Problem 26.48P

The product formed from the ring-closing metathesis of given compound is,

The synthesis of metathesis starting material using ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$, alcohols with less than five carbons, and any needed organic and inorganic reagents is,

Explanation of Solution

The given compound is a diene.

The ring-closing metathesis (RCM) by Grubbs catalyst occurs, when the starting material is diene. This reaction is facilitated under high-dilution condition as it favors intramolecular metathesis instead of intermolecular metathesis.

The product formed from the ring-closing metathesis of given compound is drawn in Figure 1.

Figure 1

The synthesis of metathesis starting material involves five steps. The first step is reaction of ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$ with $\left[\text{1}\right]\text{NaOEt}$, then with $\left[2\right]$ bromopropane to yield diethylpropylmalonate. The second step is reaction of diethylpropylmalonate with $\left[\text{1}\right]{\text{Br}}_2,hv$ then with $\left[2\right]$$\text{NaOH}$ to yield diethyl allylmalonate. The third step is treatment of diethyl allylmalonatewith $\left[\text{1}\right]\text{NaOEt}$, then with $\left[2\right]$$\text{1}$-bromopropan-$2$-ol to yield diethyl $2$-($2$-hydroxylpropyl)-$2$-propylmalonate. The fourth step is oxidation of secondary alcohol of obtained compound with $\text{PCC}$ to yield ketone. The fifth step is Wittig reaction to convert the $\text{C}=\text{O}$ bond of ketone to the $\text{C}=\text{C}$ bond of the desired product.

Figure 2

Conclusion

The product formed from the ring-closing metathesis of given compound is drawn in Figure 1. The synthesis of metathesis starting material using ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$, alcohols with less than five carbons, and any needed organic and inorganic reagents is shown in Figure 2.

Interpretation Introduction

(b)

Interpretation: The product formed from the ring-closing metathesis of given compound is to be drawn, and the synthesis of metathesis starting material using ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$, alcohols with less than five carbons, and any needed organic and inorganic reagents is to be stated.

Concept introduction: The ring-closing metathesis (RCM) by Grubbs catalyst occurs, when the starting material is diene. This reaction is facilitated under high-dilution condition as it favors intramolecular metathesis instead of intermolecular metathesis.

Answer to Problem 26.48P

The product formed from the ring-closing metathesis of given compound is,

.The synthesis of metathesis starting material using ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$, alcohols with less than five carbons, and any needed organic and inorganic reagents is,

Explanation of Solution

The given compound is a diene.

The ring-closing metathesis (RCM) by Grubbs catalyst occurs, when the starting material is diene. This reaction is facilitated under high-dilution condition as it favors intramolecular metathesis instead of intermolecular metathesis.

The product formed from the ring-closing metathesis of given compound is drawn in Figure 3.

Figure 3

The synthesis of metathesis starting material involves five steps.The first step is reaction of ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$ with $\left[\text{1}\right]\text{NaOEt}$, then with $\left[2\right]$$3$-bromoprop-$1$-ene(two equivalents) to yield diethyl $2,2$-diallylmalonate. The second step is hydrolysis of $2,2$-diallylmalonate with $\left[\text{1}\right]{\text{H}}^{+}\text{,}{\text{H}}_{\text{2}}\text{O}$ then decarboxylation with $\left[2\right]$$\Delta$ to yield hepta-$1,6$-diene. The third step is allylic bromination of hepta-$1,6$-dienewith $\text{NBS, }hv$ to yield $3$-bromohepta-$1,6$-diene. The fourth step is conversion of the $\text{Br}$ group of bromohepta-$1,6$-diene to the $\text{OH}$ group. The fifth step is protection of the $\text{OH}$ group by $\text{TBDMS}-\text{Cl}$ to yield the desired product. These steps are shown below.

Figure 4

Conclusion

The product formed from the ring-closing metathesis of given compound is drawn in Figure 3. The synthesis of metathesis starting material using ${\text{CH}}_{\text{2}}{\left({\text{CO}}_{\text{2}}\text{Et}\right)}_{\text{2}}$, alcohols with less than five carbons, and any needed organic and inorganic reagents is shown in Figure 4.