Heterocyclic compound

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For other uses of "ring structure", see Ring structure.

Structures and names of common heterocyclic compounds
Pyridine, a heterocyclic compound

A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s).[1] Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of organic heterocycles.[2]

Examples of heterocyclic compounds include all of the

FDA-approved drugs contain nitrogen heterocycles.[4]

Classification

The study of organic heterocyclic chemistry focuses especially on organic unsaturated derivatives, and the preponderance of work and applications involves unstrained organic 5- and 6-membered rings. Included are

benzene rings. For example, the fused benzene derivatives of pyridine, thiophene, pyrrole, and furan are quinoline, benzothiophene, indole, and benzofuran, respectively. The fusion of two benzene rings gives rise to a third large family of organic compounds. Analogs of the previously mentioned heterocycles for this third family of compounds are acridine, dibenzothiophene, carbazole, and dibenzofuran
, respectively.

Heterocyclic organic compounds can be usefully classified based on their electronic structure. The saturated organic heterocycles behave like the acyclic derivatives. Thus,

ethers
, with modified steric profiles. Therefore, the study of organic heterocyclic chemistry focuses on organic unsaturated rings.

Inorganic rings

Some heterocycles contain no carbon. Examples are

Hantzsch-Widman nomenclature for naming heterocyclic compounds.[5]

Notes on lists

3-membered rings

Although subject to ring strain, 3-membered a heterocyclic rings are well characterized.[6]

Three-membered rings with one heteroatom

Heteroatom Saturated Unsaturated
Boron Borirane Borirene
Nitrogen Aziridine Azirine
Oxygen
Oxirane (ethylene oxide, epoxides
) 		Oxirene
Phosphorus Phosphirane Phosphirene
Sulfur Thiirane (episulfides) Thiirene

Three-membered rings with two heteroatoms

Heteroatoms Saturated Unsaturated
2× Nitrogen Diaziridine Diazirine
Nitrogen + oxygen Oxaziridine Oxazirine
2× Oxygen Dioxirane
(highly unstable)

4-membered rings

Four-membered rings with one heteroatom

Heteroatom Saturated Unsaturated
Nitrogen Azetidine Azete
Oxygen Oxetane
Oxete
Phosphorus Phosphetane Phosphete
Sulfur Thietane Thiete

Four-membered rings with two heteroatoms

Heteroatoms Saturated Unsaturated
2× Nitrogen Diazetidine Diazete
2× Oxygen Dioxetane Dioxete
2× Sulfur Dithietane Dithiete

5-membered rings

Five-membered rings with one heteroatom

Heteroatom Saturated Unsaturated
Antimony Stibolane Stibole
Arsenic Arsolane Arsole
Bismuth Bismolane Bismole
Boron Borolane Borole
Nitrogen Pyrrolidine ("Azolidine" is not used) Pyrrole ("Azole" is not used)
Oxygen Tetrahydrofuran Furan
Phosphorus Phospholane Phosphole
Selenium Selenolane Selenophene
Silicon Silacyclopentane
Silole
Sulfur Tetrahydrothiophene Thiophene
Tellurium
Tellurophene
Tin Stannolane Stannole

Five-membered rings with two heteroatoms

The 5-membered ring compounds containing two heteroatoms, at least one of which is nitrogen, are collectively called the

Thiazoles and isothiazoles contain a sulfur and a nitrogen atom in the ring. Dithiolanes
have two sulfur atoms.

Heteroatoms Saturated Unsaturated (and partially unsaturated)
2× nitrogen Imidazolidine
Pyrazolidine 		Imidazole (Imidazoline)
Pyrazole (Pyrazoline)
Oxygen + sulfur
1,2-Oxathiolane
 Oxathiole (Oxathioline)
Isoxathiole
Nitrogen + Oxygen Oxazolidine
Isoxazolidine 		Oxazole (Oxazoline)
Isoxazole
Nitrogen + sulfur Thiazolidine
Isothiazolidine 		Thiazole (Thiazoline)
Isothiazole
2× oxygen Dioxolane
2× sulfur Dithiolane Dithiole

Five-membered rings with at least three heteroatoms

A large group of 5-membered ring compounds with three or more heteroatoms also exists. One example is the class of

dithiazoles
, which contain two sulfur atoms and one nitrogen atom.

Heteroatoms Saturated Unsaturated
N N N Triazoles
N N O Furazan
Oxadiazole
N N S
Thiadiazole
N O O Dioxazole
N S S
Dithiazole
N N N N Tetrazole
N N N N O Oxatetrazole
N N N N S Thiatetrazole
N N N N N Pentazole

6-membered rings

Six-membered rings with one heteroatom

Heteroatom Saturated Unsaturated Ions
Antimony Stibinin[7]
Arsenic Arsinane
Arsinine
Bismuth
Bismin[8]
Boron Borinane
Borinine
 Boratabenzene anion
Germanium Germinane
Germine
Nitrogen Piperidine
(Azinane is not used) 		Pyridine
(Azine is not used) 		Pyridinium cation
Oxygen
Oxane
Oxine
is not used) 		Pyrylium cation
Phosphorus Phosphinane
Phosphinine
Selenium Selenane Selenopyran[9] Selenopyrylium cation
Silicon Silinane
Siline
Sulfur Thiane Thiopyran
(2H-Thiine is not used) 		Thiopyrylium cation
Tellurium
Tellurane
 Telluropyran Telluropyrylium cation
Tin Stanninane
Stannine

Six-membered rings with two heteroatoms

Heteroatom Saturated Unsaturated
Nitrogen / nitrogen Diazinane Diazine
Oxygen / nitrogen Morpholine
Oxazine
Sulfur / nitrogen Thiomorpholine Thiazine
Oxygen / Sulfur Oxathiane Oxathiin
Oxygen / oxygen
Dioxane
 Dioxine
Sulfur / sulfur Dithiane Dithiin
Boron / nitrogen 1,2-Dihydro-1,2-azaborine

Six-membered rings with three heteroatoms

Heteroatom Saturated Unsaturated
Nitrogen Triazinane Triazine
Oxygen Trioxane
Sulfur
Trithiane

Six-membered rings with four heteroatoms

Heteroatom Saturated Unsaturated
Nitrogen Tetrazine

Carborazine is a six-membered ring with two nitrogen heteroatoms and two boron heteroatom.

Six-membered rings with five heteroatoms

Heteroatom Saturated Unsaturated
Nitrogen Pentazine

Six-membered rings with six heteroatoms

The hypothetical chemical compound with six nitrogen heteroatoms would be hexazine.

Borazine is a six-membered ring with three nitrogen heteroatoms and three boron heteroatoms.

7-membered rings

In a 7-membered ring, the heteroatom must be able to provide an empty π-orbital (e.g. boron) for "normal" aromatic stabilization to be available; otherwise, homoaromaticity may be possible. Compounds with one heteroatom include:

Heteroatom Saturated Unsaturated
Boron Borepin
Nitrogen Azepane Azepine
Oxygen Oxepane
Oxepine
Sulfur Thiepane Thiepine

Those with two heteroatoms include:

Heteroatom Saturated Unsaturated
Nitrogen Diazepane Diazepine
Nitrogen/sulfur Thiazepine

8-membered rings

Heteroatom Saturated Unsaturated
Nitrogen Azocane Azocine
Oxygen Oxocane Oxocine
Sulfur Thiocane Thiocine

Borazocine is an eight-membered ring with four nitrogen heteroatoms and four boron heteroatoms.

9-membered rings

Heteroatom Saturated Unsaturated
Nitrogen Azonane Azonine
Oxygen Oxonane Oxonine
Sulfur Thionane Thionine

Images of rings with one heteroatom

Saturated Unsaturated
Heteroatom Nitrogen Oxygen Sulfur Nitrogen Oxygen Sulfur
3-atom ring Aziridine
Oxirane
 Thiirane Azirine Oxirene Thiirene
Structure of aziridine Structure of oxirane Structure of thiirane Structure of azirine Structure of oxirene Structure of thiirene
4-atom ring Azetidine Oxetane Thietane Azete
Oxete
 Thiete
Structure of acetidine Structure of oxetane Structure of thietane Structure of azete Structure of oxete Structure of thiete
5-atom ring Pyrrolidine
Oxolane
Thiolane
 Pyrrole Furan Thiophene
Structure of pyrrolidine Structure of oxolane Structure of thiolane Structure of pyrrole Structure of furan Structure of thiophene
6-atom ring Piperidine
Oxane
 Thiane Pyridine Pyran Thiopyran
Structure of piperidine Structure of oxane Structure of thiane Structure of pyridine Structure of pyran Structure of thiopyran
7-atom ring Azepane Oxepane Thiepane Azepine
Oxepine
 Thiepine
Structure of azepane Structure of oxepane Structure of thiepane Structure of azepine Structure of oxepine Structure of thiepine
8-atom ring Azocane Oxocane Thiocane Azocine Oxocine Thiocine
Structure of azocane Structure of oxocane Structure of thiocane Structure of azocine Structure of oxocine Structure of thiocine
9-atom ring Azonane Oxonane Thionane Azonine Oxonine Thionine
Structure of azonane Structure of oxonane Structure of thionane Structure of azonine Structure of oxonine Structure of thionine

Fused/condensed rings

Heterocyclic rings systems that are formally derived by fusion with other rings, either

carbocyclic or heterocyclic, have a variety of common and systematic names. For example, with the benzo-fused unsaturated nitrogen heterocycles, pyrrole provides indole or isoindole depending on the orientation. The pyridine analog is quinoline or isoquinoline. For azepine, benzazepine is the preferred name. Likewise, the compounds with two benzene rings fused to the central heterocycle are carbazole, acridine, and dibenzoazepine. Thienothiophene are the fusion of two thiophene rings. Phosphaphenalenes are a tricyclic phosphorus-containing heterocyclic system derived from the carbocycle phenalene
.

History of heterocyclic chemistry

The history of heterocyclic chemistry began in the 1800s, in step with the development of organic chemistry. Some noteworthy developments:[10]

  • 1818: Brugnatelli makes alloxan from uric acid
  • 1832: Dobereiner produces furfural (a furan) by treating starch with sulfuric acid
  • 1834: Runge obtains pyrrole ("fiery oil") by dry distillation of bones
  • 1906: Friedlander synthesizes indigo dye, allowing synthetic chemistry to displace a large agricultural industry
  • 1936: Treibs isolates chlorophyll derivatives from crude oil, explaining the biological origin of petroleum.
  • 1951: Chargaff's rules are described, highlighting the role of heterocyclic compounds (purines and pyrimidines) in the genetic code.

Uses

Heterocyclic compounds are pervasive in many areas of life sciences and technology.[2] Many drugs are heterocyclic compounds.[11]

See also

References

  1. IUPAC Gold Book heterocyclic compounds
  2. ^ a b Thomas L. Gilchrist "Heterocyclic Chemistry" 3rd ed. Addison Wesley: Essex, England, 1997. 414 pp.
    ISBN 0-582-27843-0
    .
  3. doi:10.1002/jhet.5570290306
    .
  4. PMID 25255204.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  5. doi:10.1351/goldbook.H02737
  6. ISBN 978-0-471-72091-1
  7. ^ "Stibinin". chemspider. Royal Society of Chemistry. Retrieved 11 June 2018.
  8. ^ "Bismin". ChemSpider. Royal Society of Chemistry. Retrieved 11 June 2018.
  9. ^ "Selenopyranium". ChemSpider. Royal Society of Chemistry. Retrieved 11 June 2018.
  10. doi:10.1021/ed063p860
    .
  11. ^ "IPEXL.com Multilingual Patent Search, Patent Ranking". www.ipexl.com. Archived from the original on 24 September 2015. Retrieved 8 September 2010.

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