Synthesis of N-containing Pharmaceuticals and Natural Molecules Flashcards

1
Q

What are the different ways that amides can be synthesised?

A
  1. Amine, acid chloride and Et3N
  2. Amine, carboxylic acid and DCC
  3. Amine, carboxylic acid and CDI
  4. Amine, carboxylic acid and T3P
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2
Q

Give the forward reaction and mechanism for amide formation via acid chloride.

A
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3
Q

Give the forward reaction and mechanism of amide synthesis via carboxylic acid and DCC.

A
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4
Q

Give the forward reaction and mechanism of amide synthesis via carboxylic acid and CDI.

A
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5
Q

Give the forward reaction and mechanism of amide synthesis via carboxylic acid and T3P.

A
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6
Q

Draw the RSA of amides.

A
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7
Q

Describe a reductive amination reaction.

A

It’s a one-pot process consisting of two steps:

  1. Imine formation from an amine and a ketone or aldehyde
  2. Reduction of the imine to form the amine
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8
Q

Give the forward reaction of reductive amination.

A
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9
Q

Give the mechanism of reductive amination.

A
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10
Q

Why is AcOH used in reductive amination?

A
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11
Q

Why is Na(CN)BH3 or NaBH(OAc)3 used instead of NaBH4?

A
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12
Q

Give the RSA for reductive amination of both secondary and tertiary amines.

How can the RSA be shortened?

A
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13
Q

Give the forward reaction and mechanism for amination of alkyl halides.

A

This is an SN2 alkylation reaction.

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14
Q

Describe the amine and alkyl halide used in amination of alkyl halide reactions.

A
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15
Q

What is the problem with amination of alkyl halide reactions?

A
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16
Q

What can be used instead of alkyl halides during amination?

A
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17
Q

How can tosylates be synthesised from alcohols?

A
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18
Q

Give the RSA for amination using alkyl halides/tosylates.

A
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19
Q

Describe SNAr.

A

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.

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20
Q

Give the forward reaction of SNAr.

A
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21
Q

Give the mechanism of SNAr.

A
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22
Q

Describe the key features of an SNAr reaction.

A
  • 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
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23
Q

What aromatic molecules can undergo SNAr?

A
  • 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
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24
Q

Give the RSA for amination of aromatic halides (SNAr).

A
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25
Q

Give the forward reaction for SNAr of halopyridines.

A

This reaction is possible for both 2- and 4-halopyridines. The N serves as the EWG.

26
Q

Give the mechanism for SNAr of halopyridines.

A
27
Q

Give the RSA of SNAr of halopyridines.

A
28
Q

Give the forward reaction for Pd-mediated amination of aromatic halides using primary amines.

A
29
Q

Give the forward reaction for Pd-mediated amination of aromatic halides using secondary amines.

A
30
Q

Compare Pd-amination vs SNAr of aromatic halides.

A
31
Q

Give the RSA for Pd-amination of aromatic halides of both secondary and tertiary amines.

A
32
Q

Give the forward reaction for Cu-mediated amination of aromatic halides.

A
33
Q

Give the RSA for Cu-mediated amination of aromatic halides.

A
34
Q

Give the forward reaction for Suzuki-Miyaura aryl-aryl coupling.

A
35
Q

Give the RSA for Suzuki-Miyaura aryl-aryl coupling.

A
36
Q

What are the two ways of synthesising aryl boronic acids and aryl boronate esters?

A
  1. Br-Li exchange and reaction with B(OMe)3
  2. Direct borylation of aryl bromides (Miyaura borylation)
37
Q

Give the reaction for Br-Li exchange and reaction with B(OMe)3 to form aryl boronic acids/aryl boronate esters.

A
38
Q

Give the reaction for Miyaura borylation of aryl bromides.

A
39
Q

Give the forward reaction for α-functionalisation of cyclic amines.

A

An unspecified mixture of diastereoisomers is produced when R2 ≠ R3.

40
Q

What are the two step in α-functionalisation of cyclic amines?

A
  1. Deprotonation
  2. Electrophile trapping
41
Q

Give the mechanism for α-functionalisation of cyclic amines.

A
42
Q

Give the forward reaction for arylation α to N in cyclic amines.

A
43
Q

Give the RSA of an alkyl cyclic amine, an alcohol cyclic amine and an aryl cyclic amine via α-functionalisation of cyclic amines.

A
44
Q

Give the forward reactions for asymmetric α-functionalisation of N-boc cyclic amines.

A
45
Q
A
46
Q

Give the RSA of asymmetric α-functionalisation of cyclic N-boc amines, making both chiral diamines.

A
47
Q

Give the forward reaction for Fischer indole synthesis.

A
48
Q

What are the three steps in the mechanism for Fischer indole synthesis?

A
  1. Formation of iminium ion and enamine
  2. [3,3]-sigmatropic rearrangement to form C-C bond (key step)
  3. Rearomatisation and loss of ‘extra’ NH2
49
Q

Give the mechanism for iminium ion and enamine formation (step 1) in Fischer indole synthesis.

A
50
Q

Give the mechanism for [3,3]-sigmatropic rearrangements to form a C-C bond (step 2) in Fischer indole synthesis.

A
51
Q

Give the mechanism for rearomatisation and loss of ‘extra’ NH2 (step 3) in Fischer indole synthesis.

A
52
Q

What regiochemistry aspects need to be considered for Fischer indole synthesis?

A
  1. The aromatic hydrazine should have only one position to react which can achieved by symmetry
  2. The ketone should be symmetrical or only have one position/side that the enamine can form (can also be achieved with aldehydes)

If not, a mixture of regioisomers will form.

53
Q

What are the three main reaction classes for Fischer indole synthesis?

A
  1. Reaction with cyclic ketones
  2. Reaction with aromatic ketones
  3. Reaction with aldehydes
54
Q

Give the RSA for Fischer indole synthesis.

A
55
Q

Give the forward reaction for benzimidazole synthesis.

A
56
Q

Give the mechanism for the cyclisation step of benzimidazole synthesis.

A
57
Q

Give the RSA for benzimidazole synthesis.

A
58
Q

Give the forward reaction for tetrazole synthesis.

A
59
Q

Give the mechanism for tetrazole synthesis.

A
60
Q

Give the RSA for tetrazole synthesis.

A