Copper‐Iodide‐ and Diorganyl‐Diselenide‐Promoted Cyclization of 2‐Alkynylphenols: Alternative Approach to 3‐Organoselanylbenzo[b]furans

Abstract

This paper describes an alternative method for the synthesis of 3‐organoselanylbenzo[b]furans through the intramolecular cyclization of 2‐alkynylphenols promoted by copper iodide and diorganyl diselenides. The cyclization reactions were carried out at room temperature in the absence of base and under air (open flask). This synthetic approach proved to be efficient with both diorganyl diselenides and 2‐alkynylphenols bearing electron‐neutral, electron‐donating, and electron‐withdrawing substituents. 2‐Phenyl‐3‐phenylselanylbenzo[b]furan was used as a synthetic precursor in organochalcogen–lithium exchange and bromination reactions, allowing the synthesis of functionalized benzo[b]furans in good yields.

Selenocystine Peptides Performance in 5‐endo‐dig Reactions

“…The electrophilic species usually employed are arylselanyl chloride, or arylselanyl iodide generated in situ from diselenides using I 2 , Fe/I 2 , KI/ m ‐CPBA system or copper(I) iodide . Copper(I) iodide has also been used as catalyst for the generation of selenium electrophile . Lewis acid (FeCl 3 ) mediated generation of selenium electrophile has been used for preparation of 3‐selanyl benzo[ b ]furans and indoles as well.…”

“…[16] Copper(I) iodide has also been used as catalyst for the generation of selenium electrophile. [17] Lewis acid (FeCl 3 ) mediated generation of selenium electrophile has been used for preparation of 3-selanyl benzo[b]furans [18] and indoles [19] as well. Very recently, Perin et al reported the synthesis of 2,3-dichalcogenyl-substituted benzo[b]chalcogenophenes employing oxone induced generation of selenium electrophile.…”

Synthesis of 3-selanylbenzo[b]furans promoted by SelectFluor®

“…5,6 Despite the recent advances in the synthesis of 3-selanylbenzo[b]furans, new electrophiles and reactional conditions were explored (Scheme 1). [7][8][9][11][12][13][14][15] Initially, the establishing work by Larock and co-workers toward the synthesis of 3-selanyl- benzo [b]furans through the intramolecular cyclization of 2-(phenylethynyl)anisole with PhSeCl in CH 2 Cl 2 at room temperature. 7 In 2009, Zeni and co-workers demonstrated the synthesis of 3-selanyl-benzo[b]furans employing PhSeBr as an active electrophile.…”

“…[11][12][13][14] More recently, Liu and co-workers reported a radical cyclization reaction using selenium powder as selenium source and AgNO 3 as catalyst in DMSO at 100 C. 15 Although, there are different methodologies to prepare 3selanyl-benzo[b]furans and other functionalized selenium compounds through the reaction between diselenides compounds with oxidant reagents or Lewis acids, alternative electrophilic selenium species should be employed to avoid metals and/or toxic reagents. [9][10][11][12][13][14][15] Furthermore, RSeCl and RSeBr, 7,8 obtained from the reaction of diselenides with SO 2 Cl 2 (or Cl 2 ) and Br 2 respectively, are commercially available and largely used as selenylating agent. However, these species present a low stability under moisture, and the high nucleophilicity of chloride and bromide leaving groups can lead to undesirable side reactions.…”

“…Although electrophilic selenium catalysis (ESC) with electrophilic uoride reagents as oxidants has been demonstrated in the functionalization of alkenes, 22 fewer knowledge about the reactivity of this selenium electrophilic species is available in the literature. 23 Based on the development of new electrophilic selenium reagents, [9][10][11][12][13][14]24 herein, we describe a metal-free synthesis of 3selanyl-benzo[b]furans under mild conditions using this very reactive electrophilic selenium species (RSe-F), generated in situ at room temperature by the reaction of diorganyl diselenides with SelectFluor® reagent (Scheme 1). Moreover, the higher reactivity of RSe-F species could be explored for the insertion of selenium moiety in other building blocks because the environmentally friendly reactional condition, and the replacing chlorine and bromine by the non-nucleophilic uorine counter ion, can partially circumvented some side reactions.…”