Scholl reaction
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| Scholl reaction | |
|---|---|
| Named after | Roland Scholl |
| Reaction type | Coupling reaction |
| Identifiers | |
| RSC ontology ID | RXNO:0000377 |
The Scholl reaction is a coupling reaction between two arene compounds with the aid of a Lewis acid and a protic acid.[1][2] It is named after its discoverer, Roland Scholl, a Swiss chemist.
In 1910 Scholl reported the synthesis of a quinone [3] and of perylene from naphthalene[4] both with aluminum chloride. Perylene was also synthesised from 1,1’-binaphthalene in 1913.[5] The synthesis of Benzanthrone was reported in 1912.[6]
The protic acid in the Scholl reaction is often an impurity in the Lewis Acid and also formed in the course of a Scholl reaction. Reagents are iron(III) chloride in dichloromethane, copper(II) chloride, PIFA and boron trifluoride etherate in dichloromethane, Molybdenum(V) chloride and lead tetraacetate with BF3 in acetonitrile.[7]
Given the high reaction temperature and the requirement for strongly acidic catalysts the chemical yield often is low and the method is not a popular one. Intramolecular reactions fare better than the intermolecular ones, for instance in the organic synthesis of 9-phenylfluorene:
Or the formation of the pyrene dibenzo-(a.1)-pyrene from the anthracene 1-phenylbenz(a)anthracene (66% yield).[8]
One study showed that the reaction lends itself to cascade reactions to form more complex polycyclic aromatic hydrocarbons [9]
In certain applications such as triphenylene synthesis this reaction is advocated as an alternative for the Suzuki reaction. A recurring problem is oligomerization of the product which can be prevented by blocking tert-butyl substituents:[7]
