1. PYRYLIUM IONS AND PYRONES
(chapt 7-9)

2. PYRYLIUM IONS
Aromatic - Reactive
Counter ion often ClO4-
c.f.:
Electron deficient ring: No react. with
electrophiles
No react. with radicals
Reaction with nucleophiles
(Reacts in cycloadditions)

3. Com. avail. (SciFinder) ca 170

4. Reactions with nucleophiles
1,2-Add. - Ring opening!
Nu: Water, alchohols, ammonia, amines,
organometallics / carbanions, Wittig reagents
hydrides
1,4-add. common on flavylium

5. Reactions with nucleophiles
ANRORC (add. of Nu., Ring Opening and Ring Closure)
More stable aromatic rings
Good yields
Availability starting material

6. Cycloadditions 3-oxidopyryliums Further transformations
to 7-membered rings

7. Reactions with Electrophiles
Pyrones
Reactions with Electrophiles
No E-fil Ar Subst

8. Reactions with Electrophiles
E-fil Ar Subst prod. by other mechanisms

9. Reactions with Nucleophiles

10. Reactions with Nucleophiles

11. Cycloadditions

12. Synthesis - Pyrylium

13. Synthesis - Pyrylium

14. Synthesis - Pyrones

15. Natural products etc. Flavylium Anthocyanines:
- Gycosides of polyhydroxyflavylium (Aglycon = anthocyanidin)
- Colored (red / violet / blue) pigments, red / blue flowers, blueberries, grapes (red wine) etc.
- Antioxidants - Polyphenols - Radical scavengers

16. Natural products etc. Kawapyrones: - Isolated from Káwa
- Relaxing drug used in Polynesia
Flavonoids:
- Gycosides of polyhydroxyflavon
- Colored (yellow) pigments in plants
- Antioxidants Polyphenols - Radical scavengers
Rothenone
-Insecticide
-Parasites in rivers

17. Natural products etc. Psoralenes Isolated from various plants
-Photochemotherapy against psoriasis
-[2+2] cycloadd. with cytosin / thymin in DNA

18. -Anticoagulant - Vit K antagonist -Sweet clower disease Sweet clover
Dicoumarol
-Anticoagulant - Vit K antagonist
-Sweet clower disease
Sweet clover
(Melilotus
officinalis)
Warfarin - Marevan®
Aflatoxines
-From Aspergillus flavus (fungus)
Attacks nuts etc.
-Carcinogenic