A new strategy for the synthesis of 3,5-disubstituted phenols is established through one-pot Robinson annulation of α,β-unsaturated ketones with α-fluoro-β-ketoesters followed by in situ dehydrofluorination and tautomerization. This method has been extended to the synthesis of polysubstituted phenols and applied in the preparation of biologically active compounds.
New Syntheses of Alkylaryl and Diaryl Disubstituted Phenols and Ethyl Salicylates The sodium acetate- or triethylamine-catalyzed reaction of the chalcones and chalcone analogues 1a-n with 1-(2-oxopropyl)pyridinium chloride (2) or 1-(3-ethoxycarbonyl-2-oxopropyl)pyridinium bromide (3) gives the 3,5-disubstituted phenols (6a-g) or the 4,6-disubstituted ethyl 2-hydroxybenzoates (7a-1) in yields from 25 to 83α. Both reactions fail for chalcones with one o-substituted aryl substituent or for p,p′-dinitro-substituted diarylchalcones.
Polymer-supported preparation of substituted phenols: A new example of simultaneous cyclization-cleavage reaction on solid phase
作者:Alan R Katritzky、Sergei A Belyakov、Yunfeng Fang、John S Kiely
DOI:10.1016/s0040-4039(98)01771-7
日期:1998.10
A series of variously substituted phenols was synthesized in high yields using the “cyclization-cleavage” approach. Base-catalyzed reactions between α,β-unsaturated ketones and polymer-bound acetonyl groups result in a tandem Michael addition/annulation reaction followed by elimination and rearrangement into phenols. Since all intermediates are on the resin until the last stage, the final reaction