Reaction with electrophiles - Protonation

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Presentation transcript:

Reaction with electrophiles - Protonation PYRROLES Reaction with electrophiles - Protonation Protonated pyrroles ≈ iminium ions Reactive intermediates in many react.

Reaction with electrophiles - E-fil Ar. Subst. Nitration Sulfonation Halogenation FC-acylation (FC-alkylation)

Reaction with electrophiles - E-fil Ar. Subst. -Halogenation Haloindoles (esp. 2-halo-) unstable

Reaction with electrophiles - E-fil Ar. Subst. -Acylation

Reaction with electrophiles - E-fil Ar. Subst. -Alkylation Low reactivity, unselective, polymerization etc

Reaction with electrophiles - Condensation with aldehydes / ketones 2:1 adducts With electron rich arylaldehydes Indoles

Vit. B12 Application in Porphyrine Synthesis Hemoglobine Myoglobine Cytochromes

Application in Porphyrine Synthesis

Reaction with electrophiles - Condensation with Imines / Iminum Ions Pyrrole punstable in acidic media

Reaction with electrophiles - Condensation with Imines / Iminum Ions Mannich react. Vilsmeier react. (Vilsmeier-Haack): Formylation

Reaction with nucleophiles Electron rich ring - not very reactive towards Nu Indole: React. In benzene ring prefered Reaction with base and further react. with E-files N-alkylation favoured by: Ionic N-Met bond (Li) High solvating power of solvent (DMF, DMSO etc., crown ethers, PTC)

C-metallation and further react. Simple routes to 2- or 3-subst. indoles Electrophilic Palladation

Radical Reactions

Cyclo Additions Pyrrole as diene (4 component) Vinylpyrrole as diene EWG: Less interact. Between Lone pair on N and “diene” Vinylpyrrole as diene Pyrrole as dienophile (2 component) A few intramolek. ex.

Cyclo Additions Indole as diene (4 component) Vinylindole as diene No examples Vinylindole as diene Indole as dienophile (2 component)

Reaction with carbenes / carbenoids Indoles: No cyclopropanes isolated from carben(oid) react. Pyrrole / Indole Carboxylic Acids Also decarboxylation of indole carboxylic acids

Oxypyrroles Oxyindoles

Aminopyrroles Aminoindoles -Amino (not iminoform) - unstable 3-Amino - unstable

Azaindoles (Pyrrolopyridines) 5-membered ring≈ pyrrol (less electron rich) 6-membered ring≈pyridine (more electron rich)