Cyclization azido-olefin

The azido olefins 117 and 120 were cyclized to the triazolines 118 and 119 in excellent yields <2001TL9175>. This is an interesting process in that the intermediate triazolines are isolated and then photolytically decomposed to aziridines 119 and 122 in very good yields (Scheme 19). All of these aziridines were reported to be stable compounds especially to acidic conditions. This is significant in that previous examples of silyl-substituted monocyclic aziridines were quite unstable undergoing acid-catalyzed rearrangements. 

The isolation of the furoxan 107 following reaction of 1,2-dinitro-olefins 105 and sodium azide was explained by assuming addition of azide ion to the double bond, followed by elimination of nitrite ion to form l-azido-2-nitro6lefins 106. These vinyl azides could undergo loss of nitrogen concerted with cyclization to give 107. 

Keywords 2-Azido-3-arylacrylates, terminal alkenes, dichloromethane, palladium acetate, tri-fluoroacetic acid (TEA), oxygen-atmosphere, room temperature, domino reaction, intramolecular cyclization followed by olefination, 3-alkenyl indoles... 

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