M. Pharm Pharmaceutical Chemistry ppt on Organic chemistry first semester strategies to synthesize heterocyclic rings A presentation on heterocyclic chemistry

1. STRATEGIES TO SYNTHESIZE 5 & 6
MEMBERED HETEROCYCLIC RINGS
PRESENTED BY: PRESENTED TO:
PRABHJOT KAUR DR. SANT KUMAR VERMA
M. PHARMACY ( I SEM) ASSOCIATE PROFESSOR
(PH. CHEMISTRY) (DEPTT. OF PH. CHEMISTRY)

2. CLASSIFICATION OF ORGANIC COMPOUNDS
ORGANIC
COMPOUNDS
CYCLIC
COMPOUNDS
HOMOCYCLIC
COMPOUNDS
HETEROCYCLIC
COMPOUNDS
OPEN CHAIN
COMPOUNDS
STRAIGHT
CHAIN
COMPOUNDS
BRANCHED
COMPOUNDS

3. HETEROCYCLIC COMPOUNDS
• The word comes from a greek word ‘heteros’ meaning ‘different’.
• Heterocyclic compounds are those where one or more atom(s) of the ring are
heteroatoms such as N, O, P, S, etc.
• More than half of the known organic compounds are heterocyclic compounds.
• For example- Nucleic acid bases, haemoglobin, chlorophyll, vitamins, amino acids,
etc.

5. STRUCTURES OF SOME HETEROCYCLES

6. FIVE MEMBERED HETEROCYCLES
• The simplest of the five membered rings are Pyrrole, Furan and Thiophene.
• Characterized by high degree of reactivity towards substitution by electrophilic
reagents rather than addition.
• From molecular orbital standpoint, these molecules are described as consisting of
planar pentagon with sp2 hybridised carbon atom.

7. STRATEGIES TO SYNTHESIZE
1. The Paal- Knorr synthesis of Pyrrole
Diketone

8. 2. The Hantzsch synthesis of Pyrrole
2-oxopropyl propionate 1-chloropropan-2-one

9. 3. Simmons- Smith Reaction for synthesis of Thiophene
(1,1-bis(ethylthio)prop-1-en-2-
yl)(methylene)(phenyl)-l4-oxidane
2-(ethylthio)-4-phenylthiophene

10. SIX MEMBERED HETEROCYCLES
• The methane(-CH=) group in a benzene ring can be replaced by a heteroatom to
generate a six membered heterocyclic compounds.
• The departure from perfectly regular hexagonal geometry caused by the presence
of a hetero atom.
• A strong permanent dipole, traceable to the greater electronegativity of of nitrogen
compared with carbon.

11. STRATEGIES FOR SYNTHESIS
1. The Hantzsch synthesis of Pyridine

12. Mechanism-
1. Step 1:

13. 2. Step-2:

14. 2. Synthesis of Pyridine from other ring structure
1-(furan-2-yl)alkanone substituted pyridine

15. 3. Pyridazines synthesis from Maleic anhydride
furan-2,5-dione
pyridazine

16. REFERENCES
1.Bansal, R.K.; "Heterocyclic Chemistry"; Third edition; New Age International
Publishers; New Delhi, 2002.
2. Joule, J.A.; Mills, K.; "Heterocyclic Chemistry"; Fifth edition; John Wiley & Sons Ltd.;
United Kingdom, 2010.
3. Morrison, R.T.; Boyd, N.B.; Bhattacharjee, S.K.; "OrganicChemistry": Seventh edition;
Dorling Kindersley Pvt. Ltd.;New Delhi, 2013.

17. THANK YOU…