Flavones

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 C 15 H 10 O 2 . 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 :-