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

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• 作者：Alejandro Díaz-Moscoso ; Daniel Hernández-Alonso ; Luis Escobar ; Frank A. Arroyave ; Pablo Ballester
• 刊名：Organic Letters
• 出版年：2017
• 出版时间：January 6, 2017
• 年：2017
• 卷：19
• 期：1
• 页码：226-229
• 全文大小：282K
• ISSN：1523-7052

文摘

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.