Double bonds azide 1,3-dipolar cycloadditions, diene

Vogel and Delavier (26) reported a synthesis of the 6-azabicyclo[3.2.2]nonane skeleton 130 using an intramolecular azide-alkene cycloaddition strategy (Scheme 9.26). When refluxed in xylene, the azide 126 underwent an intramolecular 1,3-dipolar cycloaddition with the internal alkene. Nitrogen extrusion and subsequent rearrangement led to a mixmre of compounds 128, 129, and 130. Reactions of azides with the double bond of dienes were also used in various total syntheses of alkaloids, and will be discussed later in Section 9.2.2. 

Intramolecular 1,3-dipolar cycloadditions of azides have also been investigated as a route to the pyrrolizidine ring system. For example, ethyl 8-azidoocta-2,4-dienoate (56) was converted in high yield into the labile vinylaziildine 57 when it was heated under reflux in toluene. In other experiments it was demonstrated that activation of one of the double bonds of the diene was essential in order to achieve efficient intramolecular cycloaddition. The vinylaziridine 57 was then converted into the pyrrolizidine 58 by flash pyrolysis followed by catalytic hydrogenation of the product (Scheme 6.26). 

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