Potassium selenocyanate epoxides

Reactions leading to the formation of alkenic or a,/3-unsaturated bonds are very important in synthesis. This type of functionality is synthetically versatile, and of wide utility in the carbohydrate field. The use of sulfur reagents for conversion of sugar epoxides on vicinal disulfonates into al-kenes is well established97a 97b, and subsequent work with selenium reagents provided essentially comparable results. Thus, treatment of methyl 2,3-anhydro-4,6-0-benzylidene-a-D-mannopyranoside (219) with potassium selenocyanate in aqueous 2-methoxymethanol afforded methyl 4,6-0-benzylidene-2,3-dideoxy-a-D-ery/firo-hex-2-enopyranoside (220).27 Similarly, treatment of 5,6-anhydro-l,2-0-isopropylidene-a-D-glucofuranose (221) with potassium selenocyanate in methanol at room temperature... 

Triphenylphosphine selenide, potassium selenocyanate, 3-methyl-2-selenoxobenzothiazole sodium 0,0-diethyl phosphorotelluronate," 0,0-dialkyIphosphoroselenoic acid salts" and benzenese-lenocarboxamide, have all been reported as reagents capable of one-step deoxygenation of epoxides. 

Potassium selenocyanate in acetic anhydride reacts with epoxides to give 2-acetylamino-l,3-oxaselenole derivatives <93JCS(P2)35l>. Low yields of 1,3-oxaselenoles are obtained in the reaction of selenium with ethyne in aqueous base <89ZOR2283). 

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