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Synthesis of Novel bis -Hetaryl Pyrazoles via Cylization Reactions

Synthesis of Novel bis -Hetaryl Pyrazoles via Cylization Reactions. By Adel J. M. Haboub M.Sc In Organic Chemistry Cairo University. The Thesis consist of Two new research Project:.

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Synthesis of Novel bis -Hetaryl Pyrazoles via Cylization Reactions

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  1. Synthesis of Novel bis-Hetaryl Pyrazoles via Cylization Reactions By Adel J. M. Haboub M.Sc In Organic Chemistry Cairo University

  2. The Thesis consist of Two new research Project: 1- Reaction of hydrazonoyl halides with Bis-enaminones. A convenient route for synthesis of novel polyaza-terheterocycles. 2- A convenient synthesis of polyaza-3,4-bis-(hetaryl)-pyrazoles.

  3. The First project is Reaction of hydrazonoylHalid With Bis-enaminones. A convenient route for synthesis of novel polyaza-terheterocyles The results of this project was recently published in Journal Of Heterocyclic Chemistry, 50 , 17(2013)

  4. INTRODUCTION 1- Bis-enaminones of the general formula II have been shown in some reports, to be useful precursors for synthesis of some bis-heterocycles [22-27]. 2- Pyrazoles are an important class of heterocyclic compounds. Literature reports reveal that many synthetic pyrazole derivatives found use in various pharmaceutical, agrochemical, photographic and other fields. Examples of such synthetic pyrazole derivatives are sildenafil (Viagra), ionazlac and difenamizole.

  5. 1-Celecoxib 2-Lonazolac 3- Zubrin. All this compounds are a sulfa non-steroidal anti-inflammatory drug

  6. Objective To develop new synthetic strategy forterheterocyclesvia reaction ofbis-enaminoneswithhydrazonoyl chloride. Synthesis of Bis-Enaminones 4 : Ar = 4-XC6H4 X: a, H; b, Me; c, Cl; d, MeO

  7. Synthsies of Terheterocycles 6a-c :

  8. The other possible isomeric structure namely 3,5'-bis(pyrazolyl)ketone 7 was discarded on the basis of 1H NMR. From literature reports, we found that C-4 is the most electron rich carbon and so H-4 is expected to be more shielded than H-5 linked to C-5 which is bonded to nitrogen atom. Typically the signal of H-5 usually appears at δ 8.66-8.69 as in compound B whereas that of H-4 appears at δ 5.81-5.89 as in compound A. The 1H NMR of the synthesized products 8 showed a singlet signal at δ 8.6-9.22 ppm which identical to compound B rather than compound A.

  9. Hydrazinolysis of products:

  10. An unambiguous evidence for the observed site selectivity in the foregoing reaction of hydrazine hydrate with each of 5,6 and 7 was provided by comparison of the product 8a with a sample of 8a prepared by independent synthesis as depicted in Scheme 4

  11. Conclusion In summary, the studied reactions of hydrazonoyl halides with each of the bis-enaminones 4a-d and bis-enamine 10 proved useful for synthesis of novel terheterocycles. The mechanism and selectivity of the studied reactions were discussed.

  12. The Second project is A convenient synthesis of polyaza-3,4-bis(hetaryl)pyrazoles. The results of this project was accepted recently for publication in synthetic communications, 2011, in press

  13. Objective Our aim of this project is to prepare new Efficient Synthesis of polyaza-3,4-bis(hetaryl)pyrazoles of expected biological activity.

  14. :Reactions of bis-enaminone 4 with nitrogen nucleophiles d 6.83,8.42 J= 2.1Hz 6 5 Scheme 2

  15. Reactions of Bis-enaminone with hydroxyl amine hydrochloride The assigned structure 6 was confirmed by the alternate synthesis of 6b as a representative example of the series prepared 7 3 A 6 Scheme 3

  16. Similarly , Bis-enaminones reacted with each of hydrazine hydrate and phenyl hydrazine afford the respective 3,3’:4,3”-terpyrazoles

  17. Reactions of bis-enaminone with 1,2,4-triazole

  18. Reactions of bis-enaminone 4 with carbon nucleophilic reagents:

  19. Reactions of bis-enaminone 4 with ethyl cyanoacetate and ethyl benzoylacetate as Carbon nucleophile

  20. Conclusion 1- The results of the present study indicate that the new studied bis-enaminones are useful precursors for the synthesis different functionalized 3,4-bis-(hetaryl)pyrazoles via their reactions with N- and C- nucleophiles. 2- In addition, they indicate that reactions of the studied enaminone are regiospecific as they yielded, in each case, one product. The terheterocycles prepared are expected to be of pharmacological interest.

  21. My Thanks to all of you for Your Attention. And I hope you enjoyed my presentation

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