I have been fascinated with selenium-containing heterocycles, particularly after seeing the Science paper that described the co-crystal structures of a couple of selenazole-containing macrocycles with p-glycoprotein (I blogged about it on January 9th). A good way of making selenazoles would go a long way because you have to admit it – these are not your average, garden-variety heterocycles. They are exotic, yet endowed with very interesting and unusual hydrophobic properties in a dense area of space. Below is a simple method of preparing selenazoles using Ishihara’s reagent. This paper attracted my attention mainly due to the ease of converting LAH into a useful selenium transfer agent. In order to prepare Ishihara’s reagent, you need to mix LAH with elemental selenium in THF under inert atmosphere. The lithium hydrogen selenide (LiAlHSeH) is formed in situ as a gray solution that can be directly used in subsequent steps. The selenazole core was prepared by Mahler through straightforward cycloisomerization of
 propargyl selenoamides prepared in
 situ using LiAlHSeH. The method is concise and user-friendly.


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