Synthesis of benzofurans via an acid catalysed transacetalisation/Fries-type O → C rearrangement/Michael addition/ring-opening aromatisation cascade of β-pyrones

Abstract

An unusual and facile approach for the synthesis of 2-benzofuranyl-3-hydroxyacetones from 6-acetoxy-β-pyrones and phenols is presented. The synthetic sequence involves a cascade transacetalisation, Fries-type O → C rearrangement followed by Michael addition and ring-opening aromatisation. The versatility of this method was further demonstrated via the synthesis of 4,4a-dihydropyrano[3,2-b]benzofuran-3-ones, furo[3,2-c]coumarins, and spiro[benzofuran-2,2'-furan]-4'-ones. The unexpected cascade event would also provide new possible considerations in the β-pyrone-involved organic synthesis.

Last Decade of Unconventional Methodologies for the Synthesis of Substituted Benzofurans

“…An unusual and facile approach for the synthesis of 2-benzofuranyl-3-hydroxyacetones from 6-acetoxy-β-pyrones and phenols was described by Ramasastry [183] (Scheme 56). The synthetic sequence involved a cascade transacetalisation, Fries-type O-C rearrangement followed by Michael addition, and ring-opening aromatization.…”

Synthesis of Elaborate Benzofuran-2-Carboxamide Derivatives through a Combination of 8-Aminoquinoline Directed C–H Arylation and Transamidation Chemistry

“…Substituents at the benzene moiety often originate from the synthetic precursor used to construct the benzofuran scaffold. Synthetic methods for assembling the benzofuran scaffold have typically involved acid-catalyzed cyclizations [11][12][13][14][15][16][17], carbonylative cyclizations via Sonogashira reactions [18][19][20][21][22][23][24], Heck-type cyclizations [25][26][27][28][29], photocyclizations [30][31][32][33][34], radical cyclizations [35][36][37][38][39], and other types of transition-metal catalyzed transformations [40][41][42][43][44][45]. When it comes to the functionalization of the furan part, there exists a considerable number of methods for directly functionalizing either the C2 or C3 position [46][47][48][49][50][51][52][53][54][55][56].…”

Influence of coordinating groups of organotin compounds on the Fries rearrangement of diphenyl carbonate

“…16,17 Fries rearrangement has been extensively used in the synthesis of organic pharmaceuticals and gradually become a research hotspot in recent years. [18][19][20][21][22] In the synthesis of DPC, organotin, organotitanium and other Lewis acids are usually used as catalysts, and the pilot-scale amplication reaction is carried out under high temperature and high pressure.…”