Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST) , Avda. Països Catalans 16, 43007 Tarragona, Spain.
ICREA , Passeig Lluís Companys 23, 08010 Barcelona, Spain.
Org Lett. 2017 Jan 6;19(1):226-229. doi: 10.1021/acs.orglett.6b03505. Epub 2016 Dec 13.
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.
带有官能化烷基链的羟芳基烷基酮通常无法与吡咯在布朗斯台德酸介导的缩合反应中生成相应的四-α 杯[4]吡咯。在酸介导的一系列具有烷基末端氯或酯基的间-（四羟基芳基）-间-四烷基杯[4]吡咯的合成中，添加甲基三烷基氯化铵会产生显著的效果。该铵盐增强了环缩合反应，并促使几乎只生成四-α 异构体。
