Azidation of alkenes

Direct 1,2-bis azidation of triisopropylsilyl enol ethers was possible when catalytic amounts of 2,2,6,6-tetramethylpiperidine-/V-oxyl (TEMPO) were used, at - 45°C. The reaction under these conditions was often highly stereoselective, since only one (trans) adduct was obtained. In contrast to the other bis azidations of alkenes, which proceed ionically or through cycloaddition, this addition is a free radical process [98], A radical pathway occurred also when cyclohexene was treated with PhIO-Me3SiN3-TEMPO the yield of 1,2-bis azide was doubled (80%) in relation to the system PhIO-AcOH-NaN3 (in both cases the trans adduct prevailed). 

Azidation of alkenes.1 Trifluoromcthancsulfonic acid is an efficient catalyst for addition of hydrazoic acid to alkenes. The reaction is also facilitated by silica gel or alumina. A further advantage is that these adsorbents can effect in situ hydrolysis of azidotrimethylsilane to hydrazoic acid, HNj. This new procedure is particularly useful for preparation of tertiary, bcnzylic, and allylic azides. 

Lead and Phenyliodoso Azides. When lead(TV) acetate and phenyliodoso derivatives are used as a catalyst for azidation of alkenic and aromatic compounds (eq 11), lead azides and phenyliodoso azides are formed as intermediates. 

---