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DIAZINES

DIAZINES. Only C-5 in pyrimidine NOT elctron def. Diazines -Reacts even less readily with electrophiles than pyridine -Reacts easily with nucleophiles (additions / substitutions) -Reacts with nucleophilic radicals (Minisci) -Reacts as dienes in DA cycloadd. (less aromatic than pyridine).

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DIAZINES

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  1. DIAZINES Only C-5 in pyrimidine NOT elctron def. Diazines -Reacts even less readily with electrophiles than pyridine -Reacts easily with nucleophiles (additions / substitutions) -Reacts with nucleophilic radicals (Minisci) -Reacts as dienes in DA cycloadd. (less aromatic than pyridine)

  2. Reactions with electrophiles -Protonation -N-alkylation -Ox. to N-oxides (H2O2, peracids) -Pract. no E-fil Ar subst. (C-5 pyrimidine) -Halogenation by add. / elim. mechanisms c.f. pyridines weaker bases than pyridine

  3. Reactions with nucleophiles Addition - Rearomatization RMet: RLi, RMgX [ox]: DDQ, KMnO4 1,2- add 1,4-add Add. av NH2- (Chichibabin)

  4. Substitution on halodiazines Nucleophiles: -ammonia / amines -thiolates -malonates etc. -water / alchohols / alchoxides Leaving groups: -halogen -OMe -SO2Me rel. soft

  5. With hard Nu: Pd-cat. couplings

  6. Metallation

  7. Radical reactions (Minisci) Cycloadditions (DA)

  8. Oxydiazines Structure - Tautomerism React. with E-files More electron rich, reacts easier with E-files than diazines “OH” o/p directing

  9. React. with Nu-files Nu Ar subst More complex mech.:

  10. Undheim - Metaphase Inhibitors Metaphase Prophase Anaphase Telophase

  11. N-Deprotonation / Alkylation O-silylation / N-alkylation

  12. N-Deprotonation / Alkylation N-alkylation / C-alkylation N-alkylation / O-alkylation

  13. C-Deprotonation / Metallation Excess base Because of NH

  14. Replacement of oxygen Halogenation Oxo  thio

  15. Cycloadditions Cancer Psoralenes - Psoriasis

  16. Aminodiazines • Exists as aminodiazines (not imino…) • -NR2 electron donor: Stronger bases • -NR2 electron donor: Participates easier in E-fil Ar subst. • Diazotation reactions • Dimroth rearrangement Dimroth

  17. Synthesis of Pyridazines Carbonyl condensations Cycloadditions

  18. Synthesis of Pyrimidines Carbonyl condensations etc. Cycloadditions

  19. Bioactive Pyrimidines DNA bases Base pairs Double a-helix

  20. Anticancer comp. Antivirals HIV (RT -inhibitors) Barbiturates (old sedatives)

  21. Synthesis of Pyrazines Carbonyl condensations etc. Bioactive Pyrazines/Pyridazines: Pteridines Bacteria synthezize folic acid

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