Chapter 23, Problem 75CP

Interpretation Introduction

Interpretation:

The structure of product A obtained for given intramolecular Heck coupling reaction should be identified.  The observed regiochemical and stereochemical outcome should be discussed.

Concept Introduction:

Heck reaction: It describes the coupling reaction between aryl, vinyl or benzyl halide and alkene in presence of $Pd$ catalyst.

    

Consider elimination reaction where alkenes are formed when alkyl halides are treated with bases via eliminating one β-proton and one α-halo group of the alkyl halide.

The product of the elimination reaction is depends upon the β-positions of alkyl halide. If the β-positions are identical and the products formed are also identical.  If the β-positions are different and the products formed are also different.  This means the double bond can form in two different regions so this type of reaction is called regioselective and the products are called as regiochemical outcomes.

If there are two different β-protons at a β-position of alkyl halide, then on the basis of stereoselectivity the trans-isomer is favored over cis-isomer.

Syn addition: When two substituents are added over double or triple bond on same side of the compound simultaneously is called syn addition.

Syn elimination: When two substituents bonded in same side of a compound gets cleaved from the substance simultaneously then the elimination is called syn elimination.