1. Nitrogen Containing Heterocycles
3-Membered Ring
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2. Nitrogen Containing Heterocycles
3-Membered Ring in our system?
How do these work?
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3. Higher Heterocycles Containing Nitrogen
Basic Ring Systems
Acid – Base Properties
Ist pKA ?
IInd pKA ?
Stability to Water, Acid and Base
Without substituents ?
With substituents ?
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4. Higher Heterocycles Containing Nitrogen
Examples of Drugs … 4-membered ring
Importance of b-lactam ring in activity …… generation of resistance!!
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5. Higher Heterocycles Containing Nitrogen
Examples of Drugs … 5-membered ring
(anti-hyperlipidemic agent)
(anti-histaminic)
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6. Higher Heterocycles Containing Nitrogen and Another Heteroatom
Five membered Rings
Acid – Base Properties
Ist pKA ?
IInd pKA ?
Why is imidazole not basic ?
pKA with greater substitution ?
Stability to Water, Acid and Base
Without substituents ?
With substituents ?
12/1/2018

7. Higher Heterocycles Containing Nitrogen and Another Heteroatom
Examples of such heterocycles in Drugs
(anti-biotic agent)
(anti-biotic agent)
(pain medication)
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8. Heterocycles Containing Sulfur
Basic Ring Systems
Examples in Drugs
(Antihistamine) (Antibiotic) (Antimalarial)
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9. Complex Heterocycles
Examples in Drugs
(Antibiotic) (Antihypertensive)
(for pneumonia) (Antihypertensive)
(Anti-infectious) (Anti-seizure)
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10. 6 Membered Nitrogen Containing Heterocycles
Examples in Drugs
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11. Barbiturates / Barbituric Acids
(Keto form)
pKA = ~4
Phenytoin
(anti-psychotic)
(Enol form)
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12. Heterocycles More Complex Unsaturated Ring Systems
6-membered and higher heterocycles
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13. Azepine diazepine oxazepine
Heterocycles
More Complex Unsaturated Ring Systems
6-membered and higher heterocycles
Azepine diazepine oxazepine
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14. 7 and 8 Membered Nitrogen Containing Heterocycles
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15. Heterocycles Electrophilic Aromatic Substitution in Heterocycles
heterocycles generally react well with electrophiles; better than benzene (except for pyridines)
their stability to metabolic enzymes is generally lower than their carbocyclic analogs
EAS occurs at the 2-position of 5-membered heterocycles
EAS occurs at the 3-position of 6-membered heterocycles
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