Isoindole

 ( Simple Aromatic Rings ) 

In organic chemistry and heterocyclic chemistry, isoindole consists of a benzene ring fused with pyrrole. The compound is an isomer of indole. Its reduced form is isoindoline. The parent isoindole is a rarely encountered in the technical literature, but substituted derivatives are useful commercially and occur naturally. Isoindoles units occur in , an important family of dyes. Some containing isoindole have been isolated and characterized.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. See for example:

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Synthesis The parent isoindole was prepared by flash vacuum pyrolysis of an N-substituted isoindoline.R. Bonnett and R. F. C. Brown "Isoindole" J. Chem. Soc., Chem. Commun., 1972, 393-395. N-Substituted isoindoles, which are easier to handle, can be prepared by dehydration of isoindoline-N-oxides. They also arise by myriad other methods, e.g., starting from xylylene dibromide (C₆H₄(CH₂Br)₂).

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Structure and tautomerism of 2-H-isoindoles 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 solution, the 2 H-isoindole tautomer predominates. It resembles a pyrrole more than a simple imine. The degree to which the 2 H predominates depends on the solvent, and can vary with the substituent in substituted isoindoles.

N-Substituted isoindoles do not engage is tautomerism and are therefore simpler to study.

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Isoindole-1,3-diones and related derivatives The commercially important phthalimide is an isoindole-1,3-dione with two carbonyl groups attached to the heterocyclic ring.

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See also

• 1,3-Disubstituted Isoindolines.
• Isoindene with nitrogen replaced by a methylene group.

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