Chapter 17, Problem 45PP

Interpretation Introduction

Interpretation:

The synthesis of the given compound should be designed by using 1,3-butadiene is the only source of carbon atoms and using other reagents.

Concept introduction:

• Dienes undergoes addition reactions with $\text{HBr}$ as similar to simple alkenes addition with $\text{HBr}$.
• There are four carbons for addition of proton in a conjugated diene, but addition of proton at C1 and C4 carbons only form the allylic carbocation. The nucleophile can attack two positions of allylic carbocation. If it is C2 carbon, then the it is called 1,2 addition of $\text{HBr}$ and if it is C4 carbon then it is called 1,4-addition of $\text{HBr}$.
• The 1,4-adduct is thermodynamic product, because the more substituted double bond is more stable.
• The Br-group of Bromo-alkene is replaced by OH-group ( ${\text{S}}_{\text{N}}2$ process) when it is treated with $\text{NaOH}$.
• The reagent $\text{PCC}$(pyridinium chlorochromate) is used to oxidize alcohol to aldehyde.    
• Diels-Alder reaction is a $\left[\text{4+2}\right]\text{ cycloaddition}$ reaction, in which a π-system having four atoms (diene) and a π-system having two atoms (dienophile) are undergoing in cycloaddition reaction and producing a substituted cyclohexene.
• The mechanism of the ring formation in the Diels-Alder reaction is drawn by using three arrows representing the shifting of π-bonds in the two π-systems in a clockwise or counter clockwise fashion, so that the ring formation will take place.
• The configuration of dienophile will be retaining in the product.
• Retro-Diels Alder reaction of a Diels-Alder product is an inverse process of Diels-Alder reaction. It will give the diene and dienophile used for the Diels-Alder reaction.  
• The mechanism of the Retro-Diels Alder reaction for the Diels-Alder product is drawn by using three arrows representing the shifting of one-π-bond and conversion of two σ-bonds to two π-bonds in the Diels-Alder product in a clockwise or counter clockwise fashion, so that the diene and dienophile will form.

To draw: the synthesis of given compound from1,3-butadiene and some other reagents.