Oxidative azidations, azidotrimethylsilane

Lead acetate azides, Pb(OAc)4 (N3)n, prepared in situ from lead tetraacetate and azidotrimethylsilane, react with alkenes to yield a variety of products, depending on the structure of the alkene 1,2-diazides. 1,2-acetoxy azides, a-azido ketones, allylic azides, and <5-oxo nitriles (by the oxidative cleavage of cyclohexene rings)97. The diazides and acetoxy azides are formed by preferential syn addition, but the diastereoselectivity (up to 3 1) is far from satisfactory with both acyclic and cyclic alkenes98,99. 

Azanaphthalene iV-oxides undergo photochemical deoxygenation reactions in benzene containing BF3 OEt2, resulting in amines in 70-80% yield these amines are important in the synthesis of heterocyclic compounds. Azidotrimethylsilane reacts with traws-1,2-epoxy alky Isilanes in the presence of BF3-OEt2 to produce (Z)-l-alkenyl azides. The cis-1,2-epoxyalkylsilanes undergo rapid polymerization in the presence of Lewis acids. 

Starting materials, like 141, which are accessible from alkenes by azido-selenenylation, afforded only in a few cases vinyl azides exclusively as shown by the example 141 142 (Scheme 5.19). In most cases, after oxidation of the vicinal phenylseleno azides and elimination reaction on the intermediate selenoxide, mixtures of allyl and vinyl azides were obtained. Ring opening of trialkylsilyl-substituted epoxides was utilized several times for stereoselective synthesis of vinyl azides. Thus, treatment of the frani -contigured oxiranes 143 with azidotrimethylsilane and boron trifluoride etherate yielded cis-conflgured products 145. This result was explained by the intermediate 144 which should undergo anti-elimination. On the other hand, when subjected to sodium azide in dimethylformamide, epoxides 146 were transformed into vinyl azides 148 via... 

Lee JG, Kwak KH (1992) Oxidation of aldehydes to aeyl azides by chromic anhydride-azidotrimethylsilane. Tetrahedron Lett 33(22) 3165-3166... 

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