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Published bySteven Edwards Modified over 6 years ago
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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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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
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Reactions with nucleophiles
Addition - Rearomatization RMet: RLi, RMgX [ox]: DDQ, KMnO4 1,2- add 1,4-add Add. av NH2- (Chichibabin)
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Substitution on halodiazines
Nucleophiles: -ammonia / amines -thiolates -malonates etc. -water / alchohols / alchoxides Leaving groups: -halogen -OMe -SO2Me rel. soft
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With hard Nu: Pd-cat. couplings
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Metallation
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Radical reactions (Minisci)
Cycloadditions (DA)
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Oxydiazines Structure - Tautomerism React. with E-files
More electron rich, reacts easier with E-files than diazines “OH” o/p directing
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React. with Nu-files Nu Ar subst More complex mech.:
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Undheim - Metaphase Inhibitors
Prophase Anaphase Telophase
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N-Deprotonation / Alkylation
O-silylation / N-alkylation
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N-Deprotonation / Alkylation
N-alkylation / C-alkylation N-alkylation / O-alkylation
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C-Deprotonation / Metallation
Excess base Because of NH
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Replacement of oxygen Halogenation Oxo thio
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Cycloadditions Cancer Psoralenes - Psoriasis
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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
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Synthesis of Pyridazines
Carbonyl condensations Cycloadditions
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Synthesis of Pyrimidines
Carbonyl condensations etc. Cycloadditions
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Bioactive Pyrimidines
DNA bases Base pairs Double a-helix
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Anticancer comp. Antivirals HIV (RT -inhibitors)
Barbiturates (old sedatives)
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Synthesis of Pyrazines
Carbonyl condensations etc. Bioactive Pyrazines/Pyridazines: Pteridines Bacteria synthezize folic acid
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