Question

Using your roadmaps as a guide, show how to convert (2-bromoethyl)benzene into 2-chloro-1-phenylethanone. Show all reagents and all molecules synthesized along the way.

Short answer

Answer: The conversion involves two main steps. First, use the Corey-Fuchs reaction to convert (2-bromoethyl)benzene to 2-phenyl acetaldehyde by treating with n-BuLi, P(OEt)_3, NBS, and H_3O^+. Then, convert 2-phenyl acetaldehyde to 2-chloro-1-phenylethanone using DMPU and SOCl_2.

Step-by-step solution

Identify the target molecule and starting material

First, let us examine the structure of the target molecule: 2-chloro-1-phenylethanone. This molecule has a phenyl group, which is connected to a carbonyl group (C=O), and a chloro group is connected to the adjacent carbon. The starting material is (2-bromoethyl)benzene, which has a phenyl group and a bromine atom on the adjacent carbon atom.

Convert (2-bromoethyl)benzene to 2-phenyl acetaldehyde

To reach the target molecule from the starting material, we first need to convert the bromine to aldehyde. To do this, we will use the Corey-Fuchs reaction, which involves two steps: 1. Treat (2-bromoethyl)benzene with n-BuLi (n-butyllithium) and triethyl phosphite (P(OEt)_3) to generate an alkenyl phosphonate. 2. The alkenyl phosphonate is then oxidized using an organic oxidant like NBS (N-bromosuccinimide) followed by hydrolysis with H_3O^+ to give the corresponding aldehyde. Reaction: (2-Bromoethyl)benzene + n-BuLi + P(OEt)_3 -> intermediate alkenyl phosphonate intermediate alkenyl phosphonate + NBS + H_3O^+ -> (2-phenyl acetaldehyde)

Convert 2-phenyl acetaldehyde to 2-chloro-1-phenylethanone

Now we need to convert the aldehyde group to a carbonyl group and introduce the chlorine atom at the desired position. To do this, we will use the mixed chlorinating agent DMPU (1,3-Dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone) in combination with SOCl_2 (thionyl chloride): Reaction: (2-phenyl acetaldehyde) + DMPU + SOCl_2 -> (2-chloro-1-phenylethanone) The final product should be 2-chloro-1-phenylethanone.