Heterocyclic Chemistry Dr. Sheppard, CHEM 4201, Fall 2014

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

Atom Identification Numbers Greek letters

Heterocyclic Nomenclature Aromatic heterocycles Plus many more

Heterocyclic Nomenclature Non-aromatic heterocycles Plus many more

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

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?

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

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?

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

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

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

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

Next… Heterocycles in nature Applications of heterocycles