Azido-selenenylation

Azido-selenenylation The introduction of a terminal azido group to an unsaturated ketone allows azacycles to be prepared. Access to pyridine derivatives from 3-butenyl ketones is particularly convenient based on azido-selenenylation because of the facile elimination of the selenenyl group after oxidation. 

Tiecco M, Testaferri L, Temperini A, Bagnoli L, Marini F, Santi C (1998) Electrophilic Azido Selenenylation of Alkenes. A Simple Synthetic Route to Racemic Taxol Side Chain Syn Comm 28 2167... 

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... 

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