Gold-catalyzed efficient synthesis of 2,4-disubstituted furans from aryloxy-enynes

Abstract

A series of (E)-1-aryloxy-1-en-3-ynes has been prepared by Sonogashira coupling of 2-bromo-3-aryloxypropenoates with terminal alkynes using Pd(PPh(3))(4) and CuI as the catalysts in Et(3)N. The resulting enynyl-aryl ethers are found to be highly applicable to the synthesis of 2,4-disubstituted furans with an ester group at C-4 position through an Au/Ag-catalyzed annulation reaction under extremely mild reaction conditions.

OH‐Directed Alkynylation of 2‐Vinylphenols with Ethynyl Benziodoxolones: A Fast Access to Terminal 1,3‐Enynes

“…Decreasing the catalyst loading to 1mol %( Table 1, entry 5) had an egative impact on product yield (81 %). Finally,avariety of solvents were investigated, however, this did not lead to further improvement of the reaction performance (Table 1, entries [6][7][8].…”

“…[1] Thed irect alkynylation of (hetero)aryl and olefinic CÀHb onds is of particular interest because the resulting (hetero)aryl alkynes and 1,3-enynes are privileged structural motifs in av ariety of biological active compounds and single-emitting components. [5][6][7] Key to success for an efficient CÀ Hb ond activation is the existence of am etal-coordinating directing group,u nder the guidance of which only one particular C À Hb ond is activated in ah ighly regioselective manner. [5][6][7] Key to success for an efficient CÀ Hb ond activation is the existence of am etal-coordinating directing group,u nder the guidance of which only one particular C À Hb ond is activated in ah ighly regioselective manner.…”

“…[2][3][4] Furthermore, they are valuable precursors for the synthesiso favariety of carbo-and heterocycles. [5][6][7] Key to success for an efficient CÀ Hb ond activation is the existence of am etal-coordinating directing group,u nder the guidance of which only one particular C À Hb ond is activated in ah ighly regioselective manner. [8] Fordirect C À Halkynylation reactions,this has led to efficient protocols for the chemoselective synthesis of 2alkynyl substituted heteroarenes.…”

Gold-Catalyzed Reactions of Specially Activated Alkynes, Allenes, and Alkenes

“…Li and coworkers reported another gold-catalyzed transformation for the formation of furan derivatives 1154 from 3-aryloxy α,β-unsaturated esters 1153 (Scheme 263, part B). 476 The role of the Au(I) complex in this transformation is 2-fold: Au(I) allows for the formation of intermediate 1155 by hydration of the substrate and then induces the cyclization of enol 1156 by alkyne activation, leading to furan 1154. This mechanistic proposal was supported by 18 O-labeling experiments.…”

Gold(I)-catalyzed formation of furans from γ-acyloxyalkynyl ketones

“…In the last decade, gold catalysts with their carbophilic character have emerged as a new tool for furan preparation. As summarized in Scheme 1, furans could now be obtained by either gold(I) or gold(III) catalysis from various types of substrates such as allenyl ketones [8–14], enynes or diynes [15–17], alkynes and sulfur ylides [18–19], alkynyl oxiranes [20–26], alkynyl ketones [27–35], alkynyl alcohols [36–46], and alkynyl ethers [47–48]. Very recently, a three-component coupling reaction toward furans catalyzed by gold(III) has been reported starting from terminal alkenes, glyoxal derivatives and secondary amines [49].…”