2.2.2.2 Betaines and Other Unusual Structures -- 2.2.3 Reactivity -- 2.2.3.1 General Topics -- 2.2.3.2 Reactions With Electrophiles and Oxidants -- 2.2.3.3 Reactions With Nucleophiles and Reducing Agents -- 2.2.3.4 Reactions Toward Free Radicals, Carbenes, Etc. -- 2.2.3.5 Cross-Coupling and Related Reactions -- 2.2.3.6 Heterocycles as Intermediates in Organic Synthesis -- 2.2.3.7 Organocatalysts -- 2.2.4 Synthesis -- 2.2.4.1 General Topics and Nonconventional Synthetic Methodologies -- 2.2.4.2 Synthetic Strategies and Individual Methods -- 2.2.4.2.1 General Problems -- 2.2.4.2.2 Synthetic Application of Photo Reactions and Alternative Energy Input -- 2.2.4.2.3 Synthetic Application of Metal-Catalyzed Reactions -- 2.2.4.2.4 Synthesis of Heterocycles via Cycloaddition and Multicomponent Reactions -- 2.2.4.2.5 Miscellaneous Methods -- 2.2.4.3 Versatile Synthons and Specific Reagents -- 2.2.4.4 Ring Synthesis From Nonheterocyclic Compounds -- 2.2.5 Properties and Applications (Except Drugs and Pesticides) -- 2.2.5.1 Dyes and Intermediates -- 2.2.5.2 Substances With Luminescent and Related Properties -- 2.2.5.3 Organic Conductors and Photovoltaics -- 2.2.5.4 Coordination Compounds -- 2.2.5.5 Polymers -- 2.2.5.6 Ionic Liquids -- 2.2.5.7 Miscellaneous -- 2.3 Specialized Heterocycles -- 2.3.1 Nitrogen Heterocycles (Except Alkaloids) -- 2.3.2 Oxygen Heterocycles -- 2.3.3 Sulfur Heterocycles -- 2.4 Natural and Synthetic Biologically Active Heterocycles -- 2.4.1 General Sources and Topics -- 2.4.1.1 Biological Functions of Natural and Synthetic Bioactive Heterocycles -- 2.4.1.2 General Approaches to Syntheses of Biologically Active Heterocycles -- 2.4.1.3 Total Syntheses of Natural Products -- 2.4.2 Alkaloids -- 2.4.2.1 General -- 2.4.2.2 Synthesis -- 2.4.2.3 Individual Groups of Alkaloids -- 2.4.3 Antibiotics -- 2.4.4 Vitamins -- 2.4.5 Drugs -- 2.4.5.1 General.

2.4.5.2 Definite Types of Activity -- 2.4.5.2.1 Antibacterial Activity -- 2.4.5.2.2 Antitumor Activity -- 2.4.5.2.3 CNS Targeted Drugs -- 2.4.5.2.4 Anti-HIV Activity -- 2.4.5.2.5 Antimalarial and Related Activity -- 2.4.5.2.6 Remedies for Treatment of Heart Diseases -- 2.4.5.2.7 Receptor Antagonisting and Relative Activities -- 2.4.5.3 Individual Substances and Groups of Compounds -- 2.4.6 Miscellaneous -- 2.4.6.1 Enzymes, Coenzymes, and Their Models -- 2.4.6.2 Amino Acids and Peptides -- 2.4.6.3 Plant Metabolites -- 2.4.6.4 Heterocycles Produced by Marine Organisms -- 3. THREE-MEMBERED RINGS -- 3.1 One Heteroatom -- 3.1.1 One Nitrogen Atom -- 3.1.2 One Oxygen Atom -- 3.2 Two Heteroatoms -- 4. FOUR-MEMBERED RINGS -- 4.1 One Nitrogen Atom -- 4.2 One Oxygen or Sulfur Atom -- 5. FIVE-MEMBERED RINGS -- 5.1 One Heteroatom -- 5.1.1 One Nitrogen Atom -- 5.1.1.1 Monocyclic Pyrroles -- 5.1.1.2 Hydropyrroles -- 5.1.1.3 Porphyrins and Related Systems -- 5.1.1.4 Indoles, Carbazoles, Related Systems, and Hydrogenated Derivatives -- 5.1.1.5 Isoindoles (Including Phthalocyanins and Porphyrazines) -- 5.1.2 One Oxygen Atom -- 5.1.2.1 Furans -- 5.1.2.2 Annulated Furans -- 5.1.2.3 Five-Membered Lactones -- 5.1.3 One Sulfur Atom -- 5.2 Two Heteroatoms -- 5.2.1 Two Nitrogen Atoms -- 5.2.1.1 Pyrazoles and Annulated Pyrazoles -- 5.2.1.2 Imidazoles and Annulated Imidazoles -- 5.2.2 One Nitrogen and One Oxygen Atom -- 5.2.2.1 1,2-Heterocycles -- 5.2.2.2 1,3-Heterocycles -- 5.2.3 One Nitrogen and One Sulfur Atom -- 5.3 Three Heteroatoms -- 5.3.1 Three Nitrogen Atoms -- 5.3.2 Two Nitrogen Atoms and One Oxygen, Sulfur, or Selenium Atom -- 5.4 Four Heteroatoms -- 6. SIX-MEMBERED RINGS -- 6.1 One Heteroatom -- 6.1.1 One Nitrogen Atom -- 6.1.1.1 Pyridines -- 6.1.1.2 Pyridinium Compounds, Ylides, Pyridine N-oxides -- 6.1.1.3 Applications of Pyridines -- 6.1.1.4 Hydropyridines.

6.1.1.5 Pyridines Annulated With Carbocycles -- 6.1.1.6 Pyridines Annulated With Heterocycles -- 6.1.2 One Oxygen Atom -- 6.1.2.1 Pyrans and Hydropyrans -- 6.1.2.2 Annulated Pyrans -- 6.1.2.3 Pyrylium Compounds -- 6.2 Two Heteroatoms -- 6.2.1 Two Nitrogen Atoms -- 6.2.1.1 1,3-Heterocycles: Monocyclic Pyrimidines and Hydropyrimidines [Except Pyrimidine Nucleoside Bases and Nucleosides, and Annu ... -- 6.2.1.2 Pyrimidine Nucleoside Bases and Purines -- 6.2.1.3 Nucleotides and Nucleosides -- 6.2.1.4 Nucleic Acids -- 6.2.1.5 1,4-Heterocycles: Pyrazines and Hydropyrazines -- 6.3 Three Heteroatoms -- 7. RINGS WITH MORE THAN SIX MEMBERS -- 7.1 Seven-Membered Rings -- 7.2 Large Rings -- 7.2.1 Structure, Stereochemistry, Reactivity, Design -- 7.2.2 Synthesis -- 7.2.3 Applications -- 8. HETEROCYCLES CONTAINING UNUSUAL HETEROATOMS -- 8.1 Phosphorus Heterocycles -- 8.2 Boron Heterocycles -- 8.3 Silicon Heterocycles -- 8.4 Metallacycles -- REFERENCES -- Four -- Heterocycles Incorporating a Pentacoordinated, Hypervalent Phosphorus Atom -- 1. INTRODUCTION -- 2. HYPERVALENT PENTACOORDINATED PHOSPHORANES AND THEIR ANIONS -- 2.1 Monocyclic Phosphoranes -- 2.1.1 P-5C -- 2.1.2 P-4C-1 Heteroatom and P-3C-1H-1 Heteroatom -- 2.1.3 P-3C-2 Heteroatoms -- 2.1.4 P-2C-3 Heteroatoms -- 2.1.5 P-1C-4 Heteroatoms -- 2.1.6 P-5 Heteroatoms -- 2.2 Bicyclic Phosphoranes and Their Anions -- 2.2.1 P-5C and P-4C-1H Phosphoranes -- 2.2.2 P-4C-1 Heteroatom -- 2.2.3 P-3C-2 Heteroatom and P-3C-1 Heteroatom-1H -- 2.2.4 P-2C-3 Heteroatoms and P-2C-2 Heteroatom-1H -- 2.2.5 P-1C-4 Heteroatoms and P-1C-3 Heteroatom-1H -- 2.2.6 P-5 Heteroatoms and P-4 Heteroatoms-1H -- ACKNOWLEDGMENT -- REFERENCES -- Five -- Tautomerism and Structure of Azoles: Nuclear Magnetic Resonance Spectroscopy -- 1. INTRODUCTION -- 2. ANNULAR TAUTOMERISM OF FIVE-MEMBERED AZOLES.