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Abstract: Efficient stereoselective synthesis of (E,E)-bis(2-chlorovinyl) and (E,E)-bis(2-bromovinyl) selenides in 95–98% yield based on the reactions of selenium dihalides or monohalides with acetylene has been elaborated. Reactions of selenium tetrahalides with acetylene afford (E,E)-bis(2-halovinyl) selenides and (E)-2-halovinyl 1,2,2-trihaloethyl selenides. Convenient synthesis of (E,E)-bis(2-halovinyl) selenium dihalides in near quantitative yield has been developed. (E,E)-Bis(2-halovinyl) selenium dihalides undergo spontaneous rearrangement with the halogen migration from the selenium atom to the double bond. The previously described reactions of selenium monochloride and tetrabromide with acetylene have been reinvestigated. [Copyright &y& Elsevier]

Abstract: Highly chemo-, regio-, and stereoselective syntheses of novel organoselenium compounds from selenium dichloride or dibromide and unsaturated ethers are described. The reactions of selenium dichloride with allyl and propargyl phenyl ethers afford either annulated products or bis-adducts depending on the conditions. The first examples of annulation of 3-chloromethyl- and 3-chloromethylene-2,3-dihydro-1,4-oxaselenine to the benzene ring are reported. [Copyright &y& Elsevier]

Abstract: The reactions of selenium dichloride and dibromide with divinyl sulfone leading to novel selenium heterocycles, 2,4-bis(halomethyl)-1,3-thiaselenetane-1,1-diones and 5-halo-2-halomethyl-1,3-thiaselenolane-1,1-diones, have been studied. Under the action of silica gel or pyridine, 5-halo-2-halomethyl-1,3-thiaselenolane-1,1-diones undergo facile regioselective dehydrohalogenation into 5-halo-2-methylene-1,3-thiaselenolane-1,1-diones. [Copyright &y& Elsevier]

Regio- and stereoselective syntheses of novel unsaturated chalcogen-containing pyridine derivatives [3-(vinylsulfanyl)- and 3-(vinylselanyl)-2 H ,3 H -[1,3]thiazolo[3,2- a ]pyridin-4-ium chlorides, ethyl 3-(2-pyridinylsulfanyl)-2-propenoate, 1-phenyl-3-(2-pyridinylsulfanyl)-2-propen-1-one, allenyl 2-pyridinyl telluride] have been developed using the previously unknown electrophilic and nucleophilic reactions of 2-pyridinylsulfanyl chloride and 2-pyridinechalcogenolate anions. [ABSTRACT FROM AUTHOR]