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Diphenyl diselenide is the chemical compound with the formula (C6H5)2Se2, abbreviated Ph2Se2 This orange-coloured solid is the oxidized derivative of benzeneselenol. It is used as a source of the PhSe unit in organic synthesis.
It has a centrosymmetric structure, with an Se-Se bond length of 2.29 A.
Two reactions characteristic of Ph2Se2 are reduction and chlorination:
PhSeNa is a useful nucleophile, and can be used to introduce the phenylselenyl group by nucleophilic substitution of alkyl halides, alkyl sulfonates (mesylates or tosylates) or epoxides. The example below was taken from a synthesis of morphine.
PhSeCl is a powerful electrophile, used to introduce PhSe groups by reaction with a variety of nucleophiles, including enolates, enol silyl ethers, Grignard reagents, organolithium reagents, alkenes and amines. In the sequence below (early steps in the synthesis of Strychnofoline), a PhSe group is introduced by reaction of a lactam enolate with PhSeCl. This sequence is a powerful method for the conversion of carbonyl compounds to their α,β-unsaturated analogs.
Diphenyl diselenide itself is also a source of a weakly electrophilic PhSe group in reactions with relatively powerful nucleophiles like Grignard reagents, lithium reagents and ester enolates (but not ketone enolates or weaker nucleophiles). PhSeCl is both more reactive, and more efficient, since with Ph2Se2 half of the selenium is wasted.
Organoselenium compounds are toxic...
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Diphenyl_diselenide". A list of authors is available in Wikipedia.|