Selenium-nitrogen rings

T. M. Klapotke, Binary Selenium-Nitrogen Species and Related Compounds, in R. Steudel (ed.) The Chemistry of Inorganic Ring Systems, Elsevier, pp. 409-427 (1992). 

The quaternary salts of selenium-nitrogen heterocycles are labile to nucleophiles and can be converted to other heterocyclic systems by ring expansion [82, 103], An example is conversion of 1,2,4-selenadiazolium trifluoromethane sulfonate (67) into 1,3,5-selenadiazine (68) (Scheme 17) [104], 2,3-Dimethyl-1-benzo-l, 3-selenazolium tetrafluoroborate is readily condensed with aromatic aldehydes to 2-styrylselenazole [105] or treated with sodium hydride to give 3-methyl-2-methylene-2,3 -dihydro-1 -benzo-1,3 -selenazole [106],... 

Methylation of 2-phenylselenazolidine does not take place on nitrogen instead, on selenium causing ring opening <79HC(34)217>. 

Two relevant reviews, on meso-ionic ring systems and on selenium-nitrogen heterocycles, have been published and a three-part volume on Thiazole and Its Derivatives has appeared. Parts 1 and 2 of this volume are concerned with the chemistry of thiazole and substituted thiazoles, and the third part contains chapters on meso-ionic compounds, on cyanine dyes, and on selenazoles. 

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