Diphenyl diselenide

Diphenyl diselenide
IUPAC name

Diphenyl diselenide
Other names

Phenyl diselenide
Identifiers
CAS number 1666-13-3 Y
PubChem 15460
ChemSpider 14710 Y
RTECS number JM9152500
Jmol-3D images Image 1
Properties
Molecular formula C12H10Se2
Molar mass 312.13 g mol−1
Appearance Orange powder
Density 1.84 g/cm3
Melting point

59-61 °C
Solubility in water Insoluble
Solubility in other solvents Dichloromethane
Structure
Coordination
geometry		 90° at Se
C2 symmetry
Dipole moment 0 D
Hazards
R-phrases R23/25 R33 R50/53
S-phrases S20/21 S28 S45 S60 S61
Main hazards Toxic
Related compounds
Related compounds Ph2S2,
C6H5SeH
 Y (verify) (what is: Y/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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.

Ph2Se2 is prepared by the oxidation of benzeneselenoate, which is generated via the Grignard reagent:[1]

PhMgBr + Se → PhSeMgBr
2 PhSeMgBr + Br2 → Ph2Se2 + 2 MgBr2

It has a centrosymmetric structure, with an Se-Se bond length of 2.29 A.[2]

Reactions

Two reactions characteristic of Ph2Se2 are reduction and chlorination:

Ph2Se2 + 2 Na → 2 PhSeNa
Ph2Se2 + Cl2 → 2 PhSeCl

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.[3]

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.[4] This sequence is a powerful method for the conversion of carbonyl compounds to their α,β-unsaturated analogs.[5]

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.

Ph2Se2 + Nu− → PhSeNu + PhSe−

N-Phenylselenophtalimide (N-PSP) can be used if PhSeCl is too strong and diphenyl diselenide is too weak or wasteful.[6]

Safety

Organoselenium compounds are toxic.

References

  1. ^ Reich, H. J.; Cohen, M. L.; Clark, P. S. (1979), "Reagents for Synthesis of Organoselenium Compounds: Diphenyl Diselenide and Benzeneselenenyl Chloride", Org. Synth. 59: 141, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV6P0533 ; Coll. Vol. 6: 533 
  2. ^ . doi:10.1107/S0365110X52001349. 
  3. ^ . doi:10.1021/ja027882h. 
  4. ^ Lerchner, A.; Carreira, E. M. J. Am. Chem. Soc. 2002, 124, 14826
  5. ^ Preparation of α,β-Unsaturated Carbonyl Compounds and Nitriles by Selenoxide Elimination. Reich, H. J.; Wollowitz, S. Organic Reactions 1993, 44, 1.
  6. ^ Barrero, Alejandro F.; E. J. Alvarez-Manzaneda, R. Chahboun, M. Corttés, V. Armstrong (1999). "Synthesis and antitumor activity of puupehedione and related compounds". Tetrahedron 55 (52): 15181–15208. doi:10.1016/S0040-4020(99)00992-8.