1. Heterocyclic Rings Pyrrole

2. Importance of Pyrroles
Porphyrin
Haem (iron (II) complex)

3. Chlorophyll

4. Bilrubin: (formerly referred to as haematoidin) is the yellow breakdown product of normal heme catabolism, caused by the body's clearance of aged red blood cells which contain hemoglobin.

5. Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood.

6. 4: insect pheromone 5: amino acid proline 6: nicotine

7. Synthesis of pyrrole, Knorr Synthesis
L. Knorr, Ber. 17, 1635 (1884); Ann. 236, 290 (1886); L. Knorr, H. Lange, Ber. 35, 2998 (1902). The original Knorr synthesis employed two equivalents of ethyl acetoacetate, one of which was converted to ethyl 2-oximinoacetoacetate by dissolving it in glacial acetic acid, and slowly adding one equivalent of saturated aqueous sodium nitrite, under external cooling. Zinc dust was then stirred in, reducing the oxime group to the amine.

9. Nitrosation of aliphatic carbon atoms
The nitrosation reaction consists in the replacement of a hydrogen atom by the nitroso group with the formation of a nitroso or oximo derivative. With a few exceptions, the replacement of hydrogen on an aliphatic carbon atom requires the presence of an electron-attracting groups adjacent to the carbon to be nitrosated. Acyl, aroyl, carbonyl, carboxy, carbalkoxyl, nitrogen, cyano, imino, and aryl groups may serve as activators. Monoketones are readily converted into alpha-oximino ketones, whereas monoesters containing no other activating groups do not undergo the reaction. Victor Meyer discovered the reaction in 1873–1874.

11. Paal-Knorr Pyrrole Synthesis

12. The Hantzsch pyrrole synthesis
The Hantzsch pyrrole synthesis, named for Arthur Rudolf Hantzsch, is the chemical reaction of β-ketoesters (1) with ammonia (or primary amines) and α-haloketones (2) to give substituted pyrroles (3).
Note: direct reaction of β-ketoesters (1) with α-haloketones (2) gives furan [Fiest-Benary furan synthesis], and this can be a troublesome side reaction.

14. The Hantzsch pyrrole synthesis

15. Reactions of Pyrrole
Substitution at nitrogen, A) Metallation of Pyrrole

16. B) Formation of N-substituted pyrrole

18. Electrophilic Substitution (position 2 and 5)
The aromatic five-membered heterocycles all undergo electrophilic substitution, with a general reactivity order: pyrrole >> furan > thiophene > benzene

20. The Vilsmeier Haack reaction

21. Cycloaddition Reactions with dichlorocarbene Reimer-Tieman Reaction

22. Reimer-Tieman Reaction

24. Ring Expansion

25. Diels-Alder Reactions of pyrrole Pyrroles normally do not undergo DA reactions, Exception

26. [2 +2] Cycloaddition