Question

Question: Show how you can synthesize the following tertiary amine three different ways, each using a different secondary amine and adding the final substituent by

1. reductive amination (3 ways)
2. acylation-reduction (3 ways)

Short answer

The most useful method for synthesis of amines is the reductive amination. In this process, 1⁰ or 2⁰ alkyl group is added to the nitrogen atom. Generally, aldehyde is used to add 1⁰ alkyl group and ketone is used to add 2⁰ alkyl group.

Step-by-step solution

Reductive amination

The most useful method for synthesis of amines is the reductive amination. In this process, 1⁰ or 2⁰ alkyl group is added to the nitrogen atom. Generally, aldehyde is used to add 1⁰ alkyl group and ketone is used to add 2⁰ alkyl group.

Acylation-reduction

This is a method for synthesizing amines by acylating ammonia or an amine, and then reducing the amide.

Synthetic plan

(a) 2-phenylacetaldehyde combines with N-ethylpropan-1-amine, followed by reduction with NaBH(OAc)₃ (sodium triacetoxy borohydride)to gives N-ethyl-N-phenethylpropan-1-amine.

reaction 1
N-phenethylpropan-1-amine combines with acetaldehyde, followed by reduction withNaBH(OAc)₃ (sodium triacetoxy borohydride)gives N-ethyl-N-phenethylpropan-1-amine.

reaction 2
N-ethyl-2-phenylethanamine combines with propionaldehyde, followed by reduction with NaBH(OAc)₃ (sodium triacetoxy borohydride)gives N-ethyl-N-phenethylpropan-1-amine.

reaction 3
(b) 2-phenylacetyl chloride combines with N-ethylpropan-1-amine to give the initial product as N-ethyl-2-phenyl-N-propylacetamide, which on further reduction with lithium aluminum hydride gives the final product as N-ethyl-N-phenethylpropan-1-amine.

reaction 1
N-phenethylpropan-1-amine combines with acetyl chloride to give the initial product as N-phenethyl-N-propylacetamide, which on further reduction with lithium aluminum hydride gives the final product as N-ethyl-N-phenethylpropan-1-amine.

reaction 2
N-ethyl-2-phenylethanamine combines with propionyl chloride to give the initial product as N-ethyl-N-phenethylpropionamide, which on further reduction with lithium aluminum hydride gives the final product as N-ethyl-N-phenethylpropan-1-amine.

reaction 3