Stereoselective Synthesis of Lower and Upper Rim Functionalized Tetra‑α Isomers of Calix[4]pyrroles

Hydroxyaryl alkyl ketones with functionalized alkyl chains often fail to produce the corresponding tetra-α calix[4]­pyrroles in Brönsted acid mediated condensations with pyrrole. A remarkable effect exerted by the addition of methyltrialkylammonium chloride during the acid-mediated syntheses of a s...

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Bibliographic Details
Published in:Organic letters 2017-01, Vol.19 (1), p.226-229
Main Authors: Díaz-Moscoso, Alejandro, Hernández-Alonso, Daniel, Escobar, Luis, Arroyave, Frank A, Ballester, Pablo
Format: Article
Language:English
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Summary:Hydroxyaryl alkyl ketones with functionalized alkyl chains often fail to produce the corresponding tetra-α calix[4]­pyrroles in Brönsted acid mediated condensations with pyrrole. A remarkable effect exerted by the addition of methyltrialkylammonium chloride during the acid-mediated syntheses of a series of meso-(tetrahydroxyaryl)-meso-tetraalkylcalix­[4]­pyrroles featuring alkyl terminal chloro or ester groups is reported. The ammonium salt enhances the cyclocondensation reaction and induces the almost exclusive formation of the tetra-α isomers.
ISSN:1523-7060
1523-7052
DOI:10.1021/acs.orglett.6b03505