Facile synthesis of 2-substituted benzo[b]furans and indoles by copper-catalyzed intramolecular cyclization of 2-alkynyl phenols and tosylanilines

Abstract

A facile and inexpensive copper-catalyzed method was developed for the synthesis of 2-substituted benzo[b]furans and indoles.

DFT Study on the Gold(I)‐Catalyzed Dehydrogenative Heterocyclization of 2‐(1‐Alkynyl)‐2‐alken‐1‐ones to form 2,3‐Furan‐Fused Carbocycles: Effects of Additives C5H5NO vs. PhNO

“…What's more, Zhou et al proposed that the reaction yields can be effectively controlled by using different additives (C5H5NO (pyridine N-oxide) vs. PhNO (nitrosobenzene)) in the gold-catalyzed dehydrogenative annulation of 2-(1-alkynyl)-2-alken-1-ones under mild reaction conditions, and C5H5NO is the ideal additive for the construction of 2,3-furan-fused carbocycles. [29] The similar fact was also observed by Rong [30] and Chen [31] et al Therefore, the additives display a positive catalytic effect on the synthesis of furans with the transition-metal as a catalyst. However, the detailed mechanisms of chemical reactions affected by additives and transition-metal catalysts are not illustrated clearly up to date, which is worthy of in-depth study by the experimental and theoretical methods.…”

Applications of Ethynylanilines as Substrates for Construction of Indoles and Indole‐Substituted Derivatives

“…Later Zhouting Rong et al [35] have reported CuCl catalysed synthesis of N-tosyl-2-phenyl indole 58 (Scheme 19) from tosyl anilines 57 by intramolecular cyclization. [36] The optimized reaction condition concludes that good yields of the products can be obtained by treatment of anilines 57 with 5 mol% CuCl and 5 mol% Cs 2 CO 3 in acetonitrile solvent at near room temperature.…”

“…In 2017, Xiaoxiang Zhang et al [40] have reported Pd catalysed one pot synthesis of C2-quaternary indolin-3-ones 68 (Scheme 22) in 1,4-dioxane solvent at room temperature. [35] Here in situ generation of 1H-indole-3-sulfonates 67 took place from 2-Alkynyl Arylazides 66 and sulfonic Acids. In the reaction optimization it is observed that decreasing the temperature (90°C) lowers the yield of either intermediate or final product.…”

“…Later Zhouting Rong et al [35] . have reported CuCl catalysed synthesis of N‐tosyl‐2‐phenyl indole 58 (Scheme 19) from tosyl anilines 57 by intramolecular cyclization [36] .…”

Copper in Efficient Synthesis of Aromatic Heterocycles with Single Heteroatom

“…A step process was developed utilizing intramolecular cyclization (Scheme 44) of 2-alkynyl phenols/tosylanilines (131) to give benzo[b]furans and indole respectively at 23°C. [67] Scheme 44. Intramolecular cyclization of 2-alkynyl phenols/tosylanilines.…”