Selenides, 3-amido phenyl

More recently, these concepts have been extended to include a range of elegant amidoselenation processes. Alkenes react with benzeneselenenyl chloride and nitriles to yield 3-amido phenyl selenides in excellent yield. - Oxidative elimination of the latter provides the corresponding allylic amides (Scheme 60). Since the reaction proceeds via an episelenonium intermediate, Ae amido selenides are formed with tram stereospecificity. However, when applied to nonsymmetrical alkenes (equation 50) it only proceeds with regioselectivity. 

The synthesis of enantiopure thiazolines has been reported. The mixture of enantiomerically pure diastereoisomeric amido selenides 64, obtained from the reaction of camphorselenyl sulfate with trans alkenes, when treated with Lawesson s reagent affords a mixture of two thioamide derivatives 65a and 65b. The two diastereoisomeric thioamide selenides were easily separated by chromatography, each was then treated with phenyl selenyl chloride which caused deselenylation to occur in a stereospecific manner furnishing the thiazolines 66a and 66b in an enantiopure form <02TA429>. 

The stereospecific conversion of cyclohexene into the corresponding amido selenide 54 is illustrated in Scheme 8. These amidoselenenylation reactions are commonly employed for the preparation of allylic and saturated amides by oxidative or reductive deselenenylation. Propionitrile, butyronitrile, benzonitrile and ethyl cyanoacetate may be used in place of acetonitrile. Styrene gave poor results and other electron-rich olefins such as 1-methylcyclohexene or 2,3-di-methylbut-2-ene did not give the amidoselenenylation products. The reaction can also be effected starting from the hydroxy- or methoxyselenenylation products of alkenes, in the presence of water and trifluoromethanesulfonic acid in this case the nitriles are used in stoichiometric amounts [48c]. This methodology was employed to prepare the amidoselenenylation products of styrene, 55, and of electron-rich olefins. It was necessary, however, to replace the phenyl-... 

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