Diphenyl diselenide-ammonium persulfate

Olefins also undergo the Ritter reaction with nitriles in the presence of diphenyl diselenide, ammonium persulfate, and trifluoromethanesulfonic acid to produce oxazolines.When cyanamide is used, 2-aminooxazolines are obtained. The active electrophilic agent is phenylselenyl sulfate formed by oxidation of diphenylselenide with ammonium persulfate. The reaction is trans-stereospecific. 

Also based on an intermolecular hydroxyselenenylation reaction followed by the addition of the OH to an unsaturated group is the selenium promoted conversion of alkenyl nitriles into lactones described by Tiecco [73]. Alkenyl nitriles 107 (Scheme 16) react with PSS 16, generated from diphenyl diselenide and ammonium persulfate, in dioxane and water in the presence of trifluoro-methanesulfonic acid, to afford the hydroxyselenenylation product 108 which is in equilibrium with the protonated molecule 109. Intramolecular addition of the OH group give 110, which is easily hydrolyzed to the final lactone 111. 

The first example of this type of a catalytic conversion is indicated in Scheme 42 [123]. This refers to, y-unsaturated esters and amides 261, which, on treatment with an excess of ammonium persulfate and a catalytic amount of diphenyl diselenide, in methanol, ethylene glycol or in water, gave the addition products 262. These, by reaction with persulfate, afforded the y-alkoxy or the y-hydroxy-a, -unsaturated derivatives 263, respectively. 

Furthermore, Tiecco and co-workers have reported the conversion of j9,y-un-saturated alcohols into 2,5-dihydrofurans with a catalytic amount of diphenyl diselenide and an excess amount of ammonium persulfate in acetonitrile (Scheme 20) [22]. In all cases, excellent yields of 3-methoxycarbonyl-2,5-di-hydrofurans were obtained (90-96%) without any by-products. The cycliza-tion-elimination process of those j3,y-unsaturated alcohols capable of giving rise to stereoisomeric 2,5-dihydrofurans proceeds with high stereoselectivity. Thus, the eryfhro-unsaturated alcohols gave the frau5-2,5-dihydrofurans, whereas the f/ireo-unsaturated alcohols gave the cis derivatives. 

In 1993, Tiecco et al. reported a similar reaction for p,y-unsaturated esters, amides or nitriles with 10 mol% of diphenyl diselenide (449) and an excess of ammonium persulfate in alcohols or water to afford the y-alkoxy or y-hydroxy a,ji-unsaturated derivatives in good yields (Table 7.32) [311],... 

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