Purine is a bicyclic heterocyclic compound forming the basis of nucleic acids, coenzymes, and many pharmaceutical agents. Structure A fused bicyclic ring: pyrimidine ring fused with imidazole. Molecular formula: C₅H₄N₄ Found in DNA and RNA (adenine and guanine). Synthesis Traube Synthesis Multi-step process starting from 4,5-diaminopyrimidine, formic acid or formamide, then cyclization. Produces purine nucleus. … Read more
Pyrimidine is a six-membered heterocyclic compound with nitrogen atoms, essential in nucleic acids, drugs, and medicinal chemistry. Structure It is a six-membered aromatic heterocycle with two nitrogen atoms at positions 1 and 3. Molecular formula: C₄H₄N₂ Synthesis Biginelli Reaction (for substituted pyrimidines) Reactants: β-keto ester, aldehyde, and urea or thiourea. Conditions: Acidic catalysis, heating. Mechanism: … Read more
Azepines are seven-membered heterocyclic compounds important in medicinal chemistry and drug design for CNS and therapeutic agents. Structure These are seven-membered heterocycles with one nitrogen atom. Can be saturated or unsaturated (aromatic). There are several subclasses: Azepine (basic) Diazepine (2 N atoms – as in benzodiazepines) Thiazepine (N and S atoms) Synthesis of Azepines Ring … Read more
Reactions of Indole include electrophilic substitution, oxidation, reduction, and cyclization pathways vital in drug synthesis. Reactions of Indole Electrophilic Substitution (EAS) Very reactive at C-3 (due to resonance stabilization of carbocation intermediate). Secondarily reactive at C-2. Examples: Nitration: dilute HNO₃ → 3-nitroindole Halogenation: Br₂ → 3-bromoindole Friedel–Crafts acylation: at C-3 Vilsmeier–Haack Reaction: POCl₃/DMF → 3-formylindole … Read more
Basicity of Pyridine explains its nitrogen lone pair, resonance effects, and comparison with pyrrole and aliphatic amines. The basicity of pyridine refers to its ability to accept a proton (H⁺), which depends on the availability of its lone pair of electrons on the nitrogen atom. Structure and Basicity Pyridine is an aromatic heterocycle with the … Read more
Synthesis of Isoquinoline covers Bischler–Napieralski, Pictet–Spengler, and Pomeranz–Fritsch routes with key steps for drug design. Bischler–Napieralski Synthesis Reactants: β-Phenylethylamine + acyl chloride → Cyclization Reagents: POCl₃ or P₂O₅ (dehydrating agents) Steps: Acylation of phenylethylamine Cyclization under acidic conditions Dehydrogenation → Isoquinoline Pomeranz–Fritsch Reaction Reactants: Benzaldehyde + aminoacetaldehyde diethyl acetal Conditions: Acidic cyclization Reaction: Benzaldehyde + … Read more
Synthesis of Indole covers Fischer indole, Madelung, Bartoli, and Nenitzescu methods with key steps for medicinal chemistry. Fischer (Most common method) Reactants: Phenylhydrazine + Aldehyde or Ketone Conditions: Acidic, heat Example: Phenylhydrazine + Acetone → Indole (after cyclization and rearrangement) Mechanism: Hydrazone formation [3,3]-Sigmatropic rearrangement (Fischer) Cyclization and aromatization Bischler–Möhlau Indole Synthesis Reactants: Aniline + … Read more
Indole is a bicyclic heterocyclic compound found in tryptophan, alkaloids, and widely used in pharmaceuticals and organic synthesis. Chemical Formula of Indole: C₈H₇N Physical Properties of Indole: Property Value Appearance White to pale yellow crystals Melting Point ~52 °C Boiling Point ~254 °C Solubility Soluble in ethanol, ether, slightly in water Basicity Very weak (non-basic) … Read more
Reactions of Acridine involve electrophilic substitution, oxidation, and reduction processes important in pharmaceuticals and dyes. Reactions of Acridine Electrophilic Substitution (EAS) Preferred at positions 2 and 7 (central ring). Examples: Nitration: 2-nitroacridine (HNO₃ + H₂SO₄) Halogenation: Br₂ → 2-bromoacridine Nucleophilic Substitution (NAS) C-9 and neighboring positions can undergo substitution when activated (e.g., by halogen + … Read more
Synthesis of Acridine covers Bernthsen condensation, Ullmann coupling, and intramolecular cyclization for dyes and drug discovery. Bernthsen Synthesis (Classical Method) Reactants: Diphenylamine + Carboxylic acid (or acid anhydride) Catalyst: Zinc chloride (ZnCl₂) Conditions: High temperature (~250–270 °C) Reaction: Diphenylamine + Formic acid → Acridine + Water Mechanism: Involves Friedel–Crafts acylation, cyclization, and dehydration. From Anthranilic … Read more
