Zn/RuCl₃-Promoted Cleavage of Diselenides: An Efficient Michael Addition of Zinc Selenolates to Conjugated Alkenes in Aqueous Media

Abstract

A simple and highly efficient one-pot route to b-selenocarbonyl compounds and nitriles has been developed by Zn/RuCl 3 -catalyzed cleavage of diselenides and subsequent Michael addition of zinc selenolates to conjugated alkenes in aqueous media.Over the last three decades, many investigators have described important chemical transformations that were efficiently achieved using organoselenium reagents. Organoselenium compounds are of considerable interest because of their involvement as key intermediates in organic synthesis and use as a food supplement. 1 These compounds are no longer systematically classified as toxic and, thus, much effort is being devoted to accomplishing the synthesis of organic selenides. Although numerous reports on the synthesis of organoselenium compounds have already been published, 1,2 most of them, with the exception of three recent reports, 3 usually require the handling of unstable reagents, strongly acidic or basic reaction conditions, and two-step procedures. Hence, the development of a one-pot synthetic method using stable reagents under neutral conditions is in demand.Reductive cleavage of Se-Se bonds, especially cleavage of diphenyl or other diaryl diselenides, has attracted considerable attention due to the fact that selenide anion formed can be used for preparation of wide variety of compounds. Several reducing agents, including LiAlH 4 , NaBH 4 , Bu 3 SnH, and Na/NH 3 , have been introduced for Se-Se bond cleavage. 4Organometallic reactions in aqueous media have attracted considerable attention in organic synthesis. 5 Recently, transition-metal selenolates or complexes have been widely used in synthesis of organoselenium compounds, 6 but reports exploring zinc selenolates are rare. 3a,7 As a part of our interest in zinc chemistry, 7,8 we are in constant search for novel applications of zinc selenolates and zinc thiolates in chemical reactions. In the present paper we describe the use of zinc metal-ruthenium(III) chloride (Zn/ RuCl 3 ) 3a system for the cleavage of diselenides and in situ Michael addition of selenolate anion to a,b-unsaturated carbonyl compounds and nitriles to give the corresponding b-selenocarbonyl compounds and nitriles (Scheme 1).Simple stirring of diselenides 1 with metallic zinc dust in the presence of ruthenium(III) chloride (10 mol%) in MeCN-H 2 O (4:1) mixed solvent at 80 °C produced the zinc selenolate 2. This was followed by addition of a,bunsaturated carbonyl compounds and nitriles 3 which gave, after workup, the desired product 4 with yields ranging from 55-98% (Table 1). 9 Both diaryl and dialkyl (dibenzyl) diselenides react with a variety of conjugated alkenes by this procedure to produce the corresponding adducts. The conjugated alkenes include a,b-unsaturated ketones, aldehydes, carboxylic esters, and nitriles. The reaction of diaryl diselenides with methyl vinyl ketone (Table 1, entries 1 and 11) took place faster with higher yields than the others. a,b-Unsaturated carbonyl compounds and nitriles having substituents at either the a-(Table 1, ...

Seleno‐Michael Reaction of Stable Functionalised Alkyl Selenols: A Versatile Tool for the Synthesis of Acyclic and Cyclic Unsymmetrical Alkyl and Vinyl Selenides

“…[13] The key step of the stereoselective synthesis of 4'-selenonucleosides with antiviral activity is represented by a seleno-Michael addition. [14] β-Arylseleno carbonyl compounds are commonly prepared by addition of arylselenolates, often generated in situ upon treatment of the corresponding diselenides with Zn/RuCl 3 , [15] MeMgBr, [16] InÀ Me 3 SiCl, [17] or NaBH 4 , [18,19] to α,β-unsaturated carbonyl compounds. Alternative ways to access βphenylseleno carbonyl compounds rely on the reactivity of activated alkenes and alkynes with PhSeZnCl [20] or with a phenylselenium borane, such as PhSeBpin.…”

To Coordinate or not to Coordinate: The Special Role of Chalcogen Ether Functionalities in the Design of Twofold Functionalized Cyclopentadienyl Ligands [Cp,O,Ch (Ch = S, Se)]

“…Solvent‐ and catalyst‐free synthesis of the β‐thio ketones L1a , b , and synthesis of the β‐seleno ketone L1c …”

“…In addition to the β‐thio ketones L1a and L1b , the β‐seleno ketone L1c was synthesized following a procedure reported by Tatar et al, and NMR spectroscopic data of L1c was recollected in C 6 D 6 for reasons of comparison (Scheme ). The introduction of selenium provides further derivatization prospects and an additional NMR active nucleus for characterization.…”

“…Synthesis of L1c: L1c was synthesized according to a literature procedure . Diphenyl diselenide (0.400 g, 1.282 mmol), zinc dust (0.450 g, 6.883 mmol), and ruthenium(III)chloride hydrate (30 mg, 0.133 mmol) were suspended in 12 mL of acetonitrile and 2 mL of water.…”

“On‐Water” Michael‐Type Addition Reactions Promoted by PhSeZnCl

“…This reaction has been applied to protected α,β‐unsaturated lactones,4 in natural product synthesis,5 and in asymmetric Michael additions in the presence of an alkaloid 6. Seleno‐Michael reactions were effected by using in situ prepared selenolates starting from the corresponding diselenides in the presence of In‐TMSCl7 or Zn/RuCl 3 8 by using ceric(IV) ammonium nitrate9 in a radical process or β‐cyclodextrins10 as catalysts and benzenselenol as the nucleophile. All these procedures suffer from low yields and the disadvantage of using air‐ and moisture‐sensitive reagents such as selenols.…”