SYNTHESIS OF AROMATIC HETEROCYCLES

1
SYNTHESIS OF AROMATIC HETEROCYCLES CONSTRUCTION
OF THE RING SKELETON

• Carbonyl condensation type reactions
• Cycloadditions
• with 1,3-dipoles
• with ortho-quinodimethanes (DA type react.)
• Nitrene insertion

Carbonyl condensations
2
Strategy a) - 5-membered rings
Pyrrole
(Paal-Knorr Synthesis s 255)
Furan
Thiophene
3
Strategy a) - 6-membered rings
4
Strategy b
5-membered rings
Enol (or phenol)
6-membered rings
Enamin (or anilin)
5
1,3-Dipolar Cycloaddition
1,3-dipol
Only 5-membered rings
Alkene / alkyne
Ex. ozonolysis
6
Cycloaddition with ortho-Quinodimethanes
Electrocyclic ring opening
7
Nitrene Insertion
Generation of nitrenes
8
React. of nitrenes
9
Nitrene insertion - Heterocyclic synthesis