SHORT COMMUNICATIONSIn recent time the chemistry of selenium dihalides has been extensively developed. Selenium dihalides have been shown to be efficient and selective reagents in the synthesis of organoselenium compounds. Although neither selenium dichloride nor selenium dibromide can be isolated in the pure state [1], these reagents can be generated in situ and involved in various transformations [2][3][4][5][6][7][8][9][10][11][12][13][14].We perform systematic studies on reactions of selenium dichloride and dibromide with unsaturated compounds [5][6][7][8][9][10][11][12][13][14]. The reaction of selenium dihalides with vinyl ethers gave the corresponding Markovnikov adducts, bis(2-halo-2-organyloxyethyl) selenides, in high yield [8,9].The double C=C bond in vinyl chalcogenides is conjugated with the lone electron pair on the chalcogen atom, which largely determines chemical behavior of that bond. No such conjugation exists in the molecules of allyl chalcogenides. The reactions of selenium dichloride and dibromide with diallyl ether, diallyl sulfide, and diallyl selenide led to the formation of sixmembered heterocycles, 3,5-bis(halomethyl)-1,4-chalcogenaselenanes, whose structure corresponds to the anti-Markovnikov addition [10][11][12]. The reactions of selenium dihalides with divinyl and diallyl tellurides involved halogenation of the tellurium atom [13,14].In continuation of our studies on reactions of selenium dihalides with unsaturated chalcogenides [5][6][7][8][9][10][11][12][13][14], the present communication reports on the reaction of selenium dichloride and dibromide with allyl benzyl ether (I). The reactions were carried out in carbon tetrachloride or chloroform at room temperature, and the products were the corresponding anti-Markovnikov adducts, bis(3-benzyloxy-1-halopropan-2-yl) selenides II and III, which underwent gradual rearrangement into thermodynamically more stable Markovnikov adducts IV and V. Conditions ensuring selective formation of compounds IV and V in high yield were found.Selenides II and III are kinetically controlled products whose fraction in the mixture with Markovnikov adducts IV and V in the initial period was more than 90% (according to the NMR). The fraction of II (III) decreased while the fraction of IV (V) increased as the reaction progressed. The rearrangement in polar solvents (chloroform, acetonitrile) was faster than in carbon tetrachloride. The reaction of SeX 2 with ether I in carbon tetrachloride was more selective, whereas in chloroform a small amount of by-products (about 5%) was formed. Therefore, it is advisable to carry out the reaction in CCl 4 , while the isomerization of the anti-Markovnikov adducts gives better results in chloro-II, IV, X = Br; III, V, X = Cl.