Synthesis of Benzofurans from Sulfur Ylides and ortho‐Hydroxy‐Functionalized Alkynes

Abstract

The synthesis of benzofurans from readily accessible sulfur ylides and ortho‐hydroxy aryl alkynes is reported. The transformation proceeds through an isomerization/nucleophilic addition/cyclization/aromatization cascade. The substrate scope is very general with respect to both reactants and the products are afforded in 43–94% yield under conditions which are catalyst‐free and additive‐free.

A Comprehensive Review on Benzofuran Synthesis Featuring Innovative and Catalytic Strategies

“…Catalyst-free synthesis has gained a valuable place in novel methodologies regarding the synthesis of benzofuran derivatives. Yu et al 108 reported the catalyst-free synthesis of benzofuran heterocycles 108 by successive reactions of hydroxyl-substituted aryl alkynes 106 and sulfur ylides 107 which included the formation of isomers followed by the addition of nucleophile to generate intermediate B . The subsequent cyclization of intermediate B then led to the formation of an aromatic ring.…”

Highly efficient construction of 2,3-disubstituted indoline derivatives by [4 + 1] annulation of sulfur ylides and o-sulfonamido aldimines

“…Since the pioneering work developed by Johnson, Corey and Chaykovsky in the 1960s, namely the Johnson–Corey–Chaykovsky reaction, 7 sulfur ylides could now be used as C1, C2, and C3 synthons in various cascade annulation reactions, providing many strategies to synthesize structurally diverse carbo- and hetero-cyclic compounds. 8 The research groups of Aggarwal, 9 Tang, 10 Xiao, 11 Huang 12 and others 13 have disclosed many elegant reactions of sulfur ylides used to generate novel compounds. As part of our ongoing research program on methods to synthesize carbo- and hetero-cycles, 14 we report an efficient synthesis of 2,3-disubstituted indolines that relies on metal-free [4 + 1] cycloaddition of sulfur ylides and o -sulfonamido aldimine (Fig.…”