In organic chemistry and heterocyclic chemistry, isoindole consists of a benzene ring fused with pyrrole.[2] 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 phthalocyanines, an important family of dyes. Some alkaloids containing isoindole have been isolated and characterized.[3][4]
The parent isoindole was prepared by flash vacuum pyrolysis of an N-substituted isoindoline.[5] 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).
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 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 can vary with the substituent in substituted isoindoles.[7]
↑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. Script error: No such module "CS1 identifiers".
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↑R. Bonnett and R. F. C. Brown "Isoindole" J. Chem. Soc., Chem. Commun., 1972, 393-395. Script error: No such module "CS1 identifiers".
