m.pharm CNP

1. Flavones
By :- Kakadiya dipesh

2. Defination
• Flavones are yellow pigments which occur in
plant kingdom either in the free state or as
glycosides or assosiated with tannins.
• These are also known as anthoxanthins

3. • Chemically , flavones are hydroxylated
derivatives of 2-phenyl-4-chromone.

4. Properties of flavones
1. Yellow solids.
2. Soluble in water ,ethanol ,and dilute acid.
3. Precipetted by Lead salt.
4. With Ferric chloride , flavones gives dull
green or red brown colour.

5. General methods for the elucidation
of structure of flavones
• From analytical data and molecular weight
determination, the molecular formula of flavone has been
found to be C15H10O2.
• When acetylated, flavone does not yield any acetyl
derivative, indicating the absence of any –OH group.
•When fused with KOH, it yields phenol & benzoic acid.

6. •When flavone is boiled with alcoholic KOH solution, it
yields a mixture of four compound, salicylic acid(II),
acetophenone (III), o-hydroxyacetophenone (IV) and
benzoic acid (v).

7. •The formation of above products could be explained by
assuming the structure (I) as the correct structure of
flavone.

8. • On reaction with alchoholic KOH , the pyrone ring of
flavone are open to produce
o-hydroxydibenzoylmethane (IA) which than
undergoes scission in two different ways to yeilds
two pairs of products.

9. Synthesis of flavone
• Kostanecki’s synthesis :-

10. Robinson’s synthesis :-

11. •Modified claisen’s condensation :-

12. •Baker-Venkatraman Synnthsis :-

13. •Wheeler’s synthesis :-