Synthesis Of Polysubstituted Ethene And Heterocyclic Compounds Based On Organic Selenium Reagents

In this dissertation, preparation of polysubstituted ethene and heterocyclic compounds based on 2-hydroxyalkyl phenyl selenides andα-phenylselenopropionic acid reagents were further investigated as follow:Firstly, O-ethyl-O-vinyl phosphonates were prepared in a one-pot, two-step transformation by Mitsunobu reaction of 2-hydroxyalkyl phenyl selenides with monoethyl esters of phosphonic acid in the presence of diethyl azodicarboxylate (DEAD) and triphenyl phosphine (PPh3) followed by oxidation-elimination with 30 % hydrogen peroxide. The present method has advantages such as mild reaction condition, easy manipulation and good yield (76-82 %).Secondly, reaction of diphenyl diselenide with sodium borohydride in THF/DMF, followed by treatment with 2-chloroethanol affordedβ-phenylselenoethanol in 95 % yield, which was further treated with phenols promoted by DEAD/PPh3/DIEA (diisopropylethylamine) and subsequent oxidation-elimination with 30% hydrogen peroxide to provide a novel, convenient, wild two-step, one-pot synthetic methhod for aryl vinyl ethers in good yields (87-92 %).Finally, 5-(1-Phenylselanylethyl)-2-substituted-[1,3,4]oxadiazoles (1) in 68-75% yields were obtained through diacylhydrazination reaction ofα-phenylselenopropio- nic acid (2) with acid hydrazides in the presence of dicyclohexylcarbodiimide (DCC), followed by cyclocondensation in the presence of phosphorus oxychloride. Then treatment of above intermediates with 30% hydrogen peroxide formed 2-substituted-5-vinyl-[1,3,4]oxadiazoles (3) in 92-96 % yields based on the (1).