Isoindole
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| Preferred IUPAC name
2H-Isoindole[1] | |
| Identifiers | |
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PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |
| C8H7N | |
| Molar mass | 117.15 g/mol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Isoindole is a heterocyclic compound consisting of a benzene ring fused with pyrrole along the carbon-carbon bond furthest from its nitrogen atom.[2] The compound is an isomer of indole. Isoindoline is a hydrogenated form of isoindole. The parent compound is rarely encountered in the literature, but its derivatives (notably phthalocyanine dyes) are of significant utility and commercial value.[3] Several alkaloids containing this ring system have been isolated from plants.[4]
Synthesis
[edit]The parent isoindole was prepared by flash vacuum pyrolysis of N-(methoxycarbonyloxy)isoindoline.[5]
N-Substituted isoindoles, which are more stable than the parent compound, can be prepared by dehydration of isoindoline-N-oxides. Other starting materials, including o-xylylene dibromide (o-C6H4(CH2Br)2), may be used in their synthesis.
Structure and tautomerism of 2-H-isoindoles
[edit]Unlike indole, isoindoles exhibit noticeable alternation in the C-C bond lengths, which is consistent with their description as pyrrole derivatives fused to a butadiene.
In solutions, the 2H-isoindole tautomer predominates. It resembles a pyrrole more than a simple imine.[6] The degree to which the 2H predominates depends on the solvent and on the arrangement of substituents (for isoindole derivatives).[7]
2H-Isoindole (right) is the predominant tautomer relative to 1H-isoindole (left)
N-Substituted isoindoles do not tautomerize.
Isoindole-1,3-diones and related derivatives
[edit]The commercially important phthalimide is an isoindole-1,3-dione with two carbonyl groups attached to the heterocyclic ring.[8]
- Illustrative Isoindoline Derivatives
Pigment yellow 139, a common high performance pigment.
Pigment yellow 185, a common high performance pigment.
Copper phthalocyanine, one of the most pervasive synthetic pigments.
See also
[edit]- 1,3-Disubstituted Isoindolines.
- Isoindene with nitrogen replaced by a methylene group.
References
[edit]- ↑ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 213. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
- ↑ Gilchrist, T. L. (1987). Heterocyclic Chemistry. Longman. ISBN 0-582-01422-0.
- ↑ Heugebaert, Thomas S. A.; Roman, Bart I.; Stevens, Christian V. "Synthesis of isoindoles and related iso-condensed heteroaromatic pyrroles" Chemical Society Reviews 2012, volume 41, pp. 5626-5640. doi:10.1039/c2cs35093a
- ↑ See for example: Zhang, X.; Ye, W.; Zhao, S.; Che, C. T. (2004). "Isoquinoline and isoindole alkaloids from Menispermum dauricum". Phytochemistry. 65 (7): 929–932. doi:10.1016/j.phytochem.2003.12.004. PMID 15081297.
- ↑ R. Bonnett and R. F. C. Brown "Isoindole" J. Chem. Soc., Chem. Commun., 1972, 393-395. doi:10.1039/C39720000393
- ↑ Alan R. Katritzky; Christopher A. Ramsden; J. Joule; Viktor V. Zhdankin (2010). Handbook of Heterocyclic Chemistry. Elsevier. p. 133.
- ↑ John A. Joule; Keith Mills (2010). Heterocyclic Chemistry. John Wiley & Sons. p. 447.
- ↑ Radtke, Volker; Erk, Peter; Sens, Benno (2009). "Isoindoline pigments". In Faulkner, Edwin B.; Schwartz, Russell J. (eds.). High Performance Pigments (2nd ed.). Wiley-VCH. pp. 221–241. doi:10.1002/9783527626915.ch14. ISBN 978-3-527-62691-5.