1. Heterocyclic Chemistry
Dr. Sheppard, CHEM 4201, Fall 2014

2. Heterocyclic Chemistry
The chemistry of heterocycles
Formation
Reactions
Applications
Several examples already seen this semester

3. Atom Identification
Numbers
Greek letters

4. Heterocyclic Nomenclature
Aromatic heterocycles
Plus many more

5. Heterocyclic Nomenclature
Non-aromatic heterocycles
Plus many more

6. Reactions of Non-aromatic Heterocyclic Molecules
Behave like acyclic conterparts
Piperidine and pyrrolidine behave like secondary amines
Tetrahydrofuran, tetrahydropyran and dioxane behave like ethers
Solvents

7. Heteroaromatic structure
What is the hybridization of the N on pyrrolidine?
What is the hybridization of the N on pyrrole?
Which electrons in pyridine are involved in the aromatic system?

8. Common Reactions of Aromatic Heterocyclic Molecules
Acid-base reactions
Reduction
Oxidation
Usually accompanied by ring opening

9. Common Reactions of Aromatic Heterocyclic Molecules
Electrophilic aromatic substitution
Why beta-substitution with pyridine?
Can reaction also occur on nitrogen of pyridine?
Where will substitution occur with pyrrole? a? b? H?

10. Common Reactions of Aromatic Heterocyclic Molecules
Nucleophilic substitution
Not as common with benzene

11. Common Reactions of Aromatic Heterocyclic Molecules
Nucleophilic substitution
Need EWG ortho or para to leaving group to stabilize negative charge on intermediate

12. Common Reactions of Aromatic Heterocyclic Molecules
Nucleophilic substitution
More common with heterocycles
Pyridine
a and g substitution
b has no charge delocalization onto N

13. Common Reactions of Aromatic Heterocyclic Molecules
Cycloadditions
Traditional Diels-Alder
Azides and derivatives

14. Next…
Heterocycles in nature
Applications of heterocycles