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1,3-AZOLES

1,3-AZOLES. Reactivity towards E-files. Reaction with electrophiles on N - Protonation. Taut.:. Reaction with electrophiles on N N-Alkylation. Reaction with electrophiles on N N-Acylation. Only rel. for imidazole. Reaction with electrophiles on C - protonation. Slow react

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1,3-AZOLES

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  1. 1,3-AZOLES Reactivity towards E-files

  2. Reaction with electrophiles on N - Protonation Taut.:

  3. Reaction with electrophiles on N N-Alkylation

  4. Reaction with electrophiles on N N-Acylation Only rel. for imidazole

  5. Reaction with electrophiles on C - protonation Slow react Reactivity C-5 > C4 > C2 Neutral / basic cond. - Faster excange

  6. Reaction with electrophiles on C - Nitration

  7. Reaction with electrophiles on C - Nitration Reaction with electrophiles on C - Acylation No Lewis acid cat react. (Friedel Craft, basic N)

  8. Reaction with electrophiles on C - Condensation react Few ex. comp. to pyrrole / thiophene / furan Reaction with Nucleophiles No Nu displacement of H (as for pyridines Some ring opening react. on oxasole

  9. Deprotonation at N - Furter reactions C-metallation - Furter reactions • Transmetallation • Coupling react

  10. Cycloaddition

  11. Alkylazoler

  12. Quartenary 1,3-Diazolium Salts

  13. Amino 1,3-azoles All as aminotautomers, all are protonated in the ring

  14. Oxy 1,3-azoles All as oxo (carbonyl) Generally low aromaticity

  15. Synthesis of 1,3-azoles Carbonyl condensations Strategy A Strategy B Especially valuable for oxazoles JOC 2003, 9093

  16. Cycloadditions carbenoid

  17. Bioactive 1,3-azoles LO from plants Epothilone A: R=H Epothilone B: R=Me From myxobacteria Potential anticancer drugs Mechanism ≈ taxol Pilokarpin (Acetylkolin agonist) Glaukom Isolert fra Pilocarpus jaborandi (Raintree) Sør-Amerika

  18. Chymotrypsin: Cleavage of peptides

  19. 1,2-AZOLES Reaction with electrophiles on N: Protonation

  20. Reaction with electrophiles on N: Alkylation and acylation Generally more difficult than with 1,3-diazoles

  21. Reaction with electrophiles on C

  22. Reaction with nucleophiles Not replacement of H Reaction with base

  23. Reaction of metallated compounds ”C-Met”: Reactivity as expected Cycloadditions No ex. Of 1,2-azoles as dienes in DA Two mechanisms Low yields

  24. Alkyl 1,2-azoles Oxy 1,2-diazoles Amino 1,2-diazoles -amino form -3 / 5-amino- ≈ anilin, diazotation etc

  25. Synthesis of 1,2-azoles Carbonyl condensations From oximes / hydrazones

  26. Cycloadditions

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