91Ó°ÊÓ

N-Bromosuccinimide (NBS) is a brominating and oxidizing agent that is used as source for bromine in radical reactions.For example allylic brominations and various electrophilic additions.

The advantage of using NBS is that it provide low-level concentration of Br₂, and bromination of double bond doesn’t compete as much, whereas Br₂tends to react with double bond to form dibromides.

Friedel craft Alkylation is an organic reaction refers to the replacement of an aromatic proton with an alkyl group.This is done through an electrophilic attack on the aromatic ring with the help of a carbocation. The Friedel-Craft alkylation reaction is also known as a method of generating alkylbenzenes by using alkyl halides as reactants.

All of these syntheses involves NBS bromination of the benzylic position of the side chain.

(a)

Synthesis of compound (a)

(b)

Synthesis of compound (b)

(c)

Synthesis of compound (c)