Stannyl azides

Azido alcohols.1 This azide is considerably more reactive for cleavage of epoxides than azidotrimethylsilane, which requires a Lewis acid promotor. Although DMF enhances the reactivity of the silyl azide, it lowers the reactivity of the stannyl azide. The reactivity of the latter azide is also decreased by neighboring ester, acetonide, or ether groups. 

In contrast, the reaction between sterically normal silyl azides and metal organyls (the same is true for germyl and stannyl azides) leads either to substitution of the silicon-bound azide group by an organyl group, or to cleavage of molecular nitrogen from the azide moiety 10) [Eq. (3)]. The preference for reaction in paths (a) or (b) of Eq. (3) depends on the kind... 

Treatment of tetrachloro- and tetrabromocyclopropene 3 with trimethylsilyl azide or tributyl-stannyl azide led to the isolation of 4,5,6-trichloro- or 4,5,6-tribromo-l,2,3-triazine 4.122 Attempts to use this method for the preparation of other 1,2,3-triazines failed.122,124... 

Chiral y-amino-acids (e.g. 180) have been prepared from the corresponding optically active /8-amino-acids by the addition of one carbon atom using the Arndt-Eistert reaction.w-Amino-acids are available from cyclic anhydrides by treatment with stannyl azide (to give an w-isocyanatocarboxylic acid) followed by addition of an alcohol. In contrast to simple enamines, oxidation of N-acyl-a-aminocrotonates with thallium nitrate leads to the corresponding a/8-dimethoxy derivatives. 

A-allylic amines are conveniently prepared in high yields by the reaction of azides with allylindium reagents in the presence of sodium iodide at ambient temperature (Equation (74)).307 Stannylation with tributylchloro-stannane occurs exclusively at the a-carbon, yielding allyltributylstannanes (E, Z)-isomerization of the allylic double bond depends largely upon the substitution pattern on the allylic moiety (Equation (75)).26 Allyl and propargyl bromides react with diphenyl diselenides in aqueous media to give allyl and propargyl selenides (Equation (76)).308 309... 

Besides the already mentioned Dimroth method [Eq. (1)], silyl-, germyl- or stannyltriazenes should also be obtainable by the direct silvlation, germylation, or stannylation of azides, as shown in Eq. (5). 

Kim reported efficient radical cyclizations involving azides as radical traps (Scheme 8.33)7 This intramolecular amination process is efficient and proceeds via a 3,3-triazenyl radical that readily eliminates nitrogen to afford an aminyl radical. The use of (TMSlsSiH gives better results than BusSnH since azides are relatively inert toward tris(trimethylsilyl) silyl radicals. However, tin hydride can be used with alkyl iodides since the iodine atom abstraction by the stannyl radical is faster than its addition to the azide. 

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