Synthesis of N-containing Pharmaceuticals and Natural Molecules Flashcards
What are the different ways that amides can be synthesised?
- Amine, acid chloride and Et3N
- Amine, carboxylic acid and DCC
- Amine, carboxylic acid and CDI
- Amine, carboxylic acid and T3P
Give the forward reaction and mechanism for amide formation via acid chloride.
Give the forward reaction and mechanism of amide synthesis via carboxylic acid and DCC.
Give the forward reaction and mechanism of amide synthesis via carboxylic acid and CDI.
Give the forward reaction and mechanism of amide synthesis via carboxylic acid and T3P.
Draw the RSA of amides.
Describe a reductive amination reaction.
It’s a one-pot process consisting of two steps:
- Imine formation from an amine and a ketone or aldehyde
- Reduction of the imine to form the amine
Give the forward reaction of reductive amination.
Give the mechanism of reductive amination.
Why is AcOH used in reductive amination?
Why is Na(CN)BH3 or NaBH(OAc)3 used instead of NaBH4?
Give the RSA for reductive amination of both secondary and tertiary amines.
How can the RSA be shortened?
Give the forward reaction and mechanism for amination of alkyl halides.
This is an SN2 alkylation reaction.
Describe the amine and alkyl halide used in amination of alkyl halide reactions.
What is the problem with amination of alkyl halide reactions?
What can be used instead of alkyl halides during amination?
How can tosylates be synthesised from alcohols?
Give the RSA for amination using alkyl halides/tosylates.
Describe SNAr.
SN2 alkylation of aryl halides is impossible as the nucleophile can’t approach from opposite the C-X bond. However, an addition-elimination reaction is possible (SNAr), as long as an EWG is on the ring. NO2 is the most powerful EWG and is commonly used.
Give the forward reaction of SNAr.
Give the mechanism of SNAr.
Describe the key features of an SNAr reaction.
- the leaving groups that work best are the most electronegative halides e.g. F, Cl
- normally, F- is not a leaving group, but here the RDS is the addition step, so more electronegative groups make this step faster
- the amine can be primary or secondary
What aromatic molecules can undergo SNAr?
- If the LG and EWG are ortho or para to each other then the reaction will work
- If they are meta to each other then the electrons can’t be delocalised onto the EWG and therefore the reaction won’t work
- This allows regioselective substitutions to occur, only the LG ortho/para to the EWG will be displaced
Give the RSA for amination of aromatic halides (SNAr).