Synthesis of bis(2-haloethyl) selenides by reaction of selenium dihalides with ethylene

Abstract

Introduction in the organic synthesis of new electrophilic reagents, selenium dichloride and dibromide, made it possible to develop effi cient methods of preparation of new organoselenium compounds [1–4]. Based on reactions of selenium dihalides with acetylene a new stereoselective method was developed for the synthesis of (Е,Е)-bis(2-halovinyl) selenides [2]. The reaction of selenium dihalides with alkenes proceeds stereoselectively leading to the formation of substituted bis-(2-haloethyl) selenides, products of addition by Markovnikoff rule or against it depending on the substituent at the double bond (electron-donor [3] or electron-acceptor [4]). Reactions of selenium dihalides with ethylene were not described in the literature. They would be applied to the direct atom economy synthesis of bis(2-haloethyl)selenides (I, II). Note that 2-haloethyl selenides are used in organic synthesis [5] and exhibit antitumor activity [6]. The published information exists on a reaction of selenium monochloride (Se2Cl2) with ethylene that results in bis(2-chloroethyl)selenium dichloride [7]. The reaction with ethylene of selenium tetrahalides afforded bis(2-haloethyl)selenium dihalides [8]. Therefore the preparation of selenides I, II in one stage from ethylene and selenium monohalides or tetrahalides failed [7, 8]. We investigated the reactions of selenium dihalides with ethylene and found the conditions ensuring the preparation of selenides I, II in up to 90–94% yield and minimum of side reaction products. SeX2 + 20_25°C X Se X