The reaction of 1,2,3-selenadiazole with olefins

When 1,2,3-selenadiazoles synthesized from cyclic ketones were treated with an excess amount of olefins at 130 degrees C, the addition of a vinyl radical, which was generated in situ by the denitrogenation of 1,2,3-selenadiazoles, to a carbon-carbon double bond followed by intramolecular cyclization proceeded efficiently giving the corresponding dihydroselenophenenes in moderate to good yields along with the formation of the corresponding 1,4-diselenins and selenophenes as by-products. In this reaction, the number of carbon atoms on the cyclic ring of the ketones used as the starting materials in the synthesis of the 1,2,3-selenadiazoles plays an important role in the selectivity of the products. In contrast to the reaction of the 1,2,3-selenadiazoles prepared from the cyclic ketones, in the reaction of 1,2,3-selenadiazoles derived from aromatic and linear ketones, the dihydroselenophenene and 1,4-diselenins derivatives were not obtained and the corresponding alkynes were formed as the sole product. (C) 2000 Published by Elsevier Science S.A. All rights reserved.